# Fault Code: P2181-35-00



## Dubhaus Tuning (Apr 11, 2002)

I have a 2002 Jetta 1.8T. I ran Vag-Com and got a fault code Malfunction Cooling System P2181-35-00. Is there any other information that would be needed to find out what would be the specific problem? Hopefully, someone can shed some light on the subject.........







http://****************.com/smile/emthup.gif


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## Theresias (Feb 11, 2004)

Did you check the cooling temp sensor?


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## Dubhaus Tuning (Apr 11, 2002)

*Re: (Theresias)*

I was reading another thread that started with the same 4 numbers, but it wasn't proof positive that the cooling temp sensor was responsible. What tests can be done to check the CTS? Other things that have happened lately are that I've noticed a bit worse gas mileage and roughness in over all driveability. I thought it might be from an overdue service, but now I got the CEL. I was also told it might be the water pump, but I could check that by disconnecting the coolant return line at the reservoir.


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## Uwe (Jan 16, 2000)

*Re: (Dubhaus Tuning)*

I described some tests in this thread:
http://forums.vwvortex.com/zerothread?id=2428598
-Uwe-


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## Dubhaus Tuning (Apr 11, 2002)

*Re: (Uwe)*

Thanks. http://****************.com/smile/emthup.gif 
Another bit of information: when the CEL came on, the car was already warmed up. I was on my way to work in the morning and the car already was at normal operating temp. I was on the highway doing about 65-70ish. There seemed to be the slightest bit of a hestation when the CEL turned on. When we ran the car for codes, I erased the code and it has not turned on yet, but that was last night, so I'm not sure if I have cycled to full readiness again yet.


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## mrk130 (Nov 9, 2003)

*Re: (Dubhaus Tuning)*

***hint hint*** replace your ect sensor todd.


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## Dubhaus Tuning (Apr 11, 2002)

*Re: (mrk130)*

I replaced the ETC sensor and put some BG C5F fuel, intake cleaner in the car. Car runs MUCH better!!! So far the seems to have better fuel economy, easier all-around drivability, more power, and doesn't surge in the lower rpm's while starting off. I haven't run the car for fault codes, but I doubt they will show up anyway.
Thanks for the help guys!! http://****************.com/smile/emthup.gif


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## dpak4eva (Jan 1, 2003)

*Re: (Dubhaus Tuning)*

what is an etc sensor anyone? i have same problem w/ the code p2181.


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## Uwe (Jan 16, 2000)

*Re: (dpak4eva)*


_Quote »_what is an etc sensor

It's a typo. I'm sure "ECT" was intended. Engine Coolant Temperature.
-Uwe-


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## Abbruzzesse (May 26, 2004)

*Re: (Uwe)*

Is the Engine Coolant Temperature the replacement for p2181? What exactly is it? 
I too have p2181 going off, and they say I need to replace the temperature sensor, which will cost me 450. Thoughts? 
Also, I have had problems with p0118, which I believe is the coolant sensor. The guy told me these two things were not related. I told him no on the p2181 work. I had already had p0118 fixed, and they are fixing it again under their parts warranty.


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## 3G3T7I (Sep 30, 2005)

*Re: Fault Code: P2181-35-00 (Dubhaus Tuning)*

I've been unsuccessful resolving this code since August. When it initially occurred I changed the ECT sensor, reset the code and eventually the car established readiness. The night before it was due for inspection in October I decided to check for dtc's and although the CEL wasn't lit the code was stored. I cleared the code but couldn't get readiness so I cancelled the inspection, replaced the sensor again, waited for readiness and passed inspection. Just recently the code has reappeared. I have been logging trips back and forth to work and haven't seen any significant temp behavior. Last weekend I checked the continuity between the ECU and sensor connectors. I applied Stabilant to the connectors and so far the CEL isn't lit, but I haven't checked for a code. I'm going to wait until it out for now.


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## Abbruzzesse (May 26, 2004)

*Re: Fault Code: P2181-35-00 (3G3T7I)*

Interesting. In my scenario, I had taken it to another dealer because of the location. They, upon their diagnostic test, told me that 1) the coolant temp sensor needed to be replaced, and 2) that the connectors to the ECU were weak and that I needed a stabilitant. 
Of course, they screwed me over, because they didn't inform me that they also had to replace my CTS for free because they were a VW dealer, but they knew my history and didn't say anything about a thermostat replacement. 
How much is it to get the stablitant installed? 
Please update me about your car. I'd like to see if your method works, especially because I have had problems for two months with the MIL, but no problems with the temperature of the car or driving.


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## Uwe (Jan 16, 2000)

*Re: Fault Code: P2181-35-00 (Abbruzzesse)*

https://www.micro-tools.com/st...de=22
-Uwe-


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## turbeau3 (Jul 17, 2006)

*Re: Fault Code: P2181-35-00 (Uwe)*

i got the code p2181 also, changed the ECT sensor and the code came back. ANy i deas of what else it could be??


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## Theresias (Feb 11, 2004)

*Re: Fault Code: P2181-35-00 (turbeau3)*

http://wiki.ross-tech.com/inde...08577


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## 3G3T7I (Sep 30, 2005)

*Re: Fault Code: P2181-35-00 (3G3T7I)*

The CEL returned after being gone for almost a week, I'm going to focus on the harness if I have time this weekend. I'm starting to think it'a harness or connector issue. Fortunately the car drives as well as can be expected.


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## Abbruzzesse (May 26, 2004)

*Re: Fault Code: P2181-35-00 (3G3T7I)*

My MIL went off again. Any luck with replacing the harness or connectors? Are you trying to prevent a thermostat replacement as it would be costly and unnecessary because the car and temp is fine?
Thanks.


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## 3G3T7I (Sep 30, 2005)

*Re: Fault Code: P2181-35-00 (Abbruzzesse)*

No I haven't had time for this with the holidays and other work, brakes and rotors on the 91 and an ignition switch on the 97 etc....


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## blkmgc20 (Jul 11, 2003)

*Re: Fault Code: P2181-35-00 (3G3T7I)*

I had this p2181 fault code a while back. After clearing it, within a week it would come back on the morning commute to work. I had replaced the coolant temp sensor three times, which never fixed anything.
Finally, I replaced the thermostat and....VUALLA! Haven't seen it since. Thermostat costs 20 bucks and is not too much a pain to replace. 
So, if replacing the temp sensor doesn't work, then try the next inexpensive part: the thermostat. Hope this helps


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## 1pt8t (Mar 14, 2007)

*Re: Fault Code: P2181-35-00 (blkmgc20)*

Interesting scenario....








'03 1.8T Jetta
Water pump has been crusting out coolant for a couple months, i keep adding distilled to it, NBD. 
Driving down the highway thursday, slammed on the brakes from 75-0 mph, car is shaking violently w/ the ABS. 
CEL MIL comes on, heading home from work. Dealership next morning, says, waterpump (i told them it was leaking) has a broken impeller and seal. Thermostat is not working (temp goes up fine, pegs at 190). Estimate for thermo and pump is like $700. I had to PRY the DTC out of those AH, which is vw18613/P2181. Car is at 59,500 miles (power train lasts till 60K and transfers free of charge if bought used), they won't honor the warantee b/c i don't have every service record b/f i bought the car, anybody else experienced this? 
So i'm like wtf mate? Tracked down a waterpump ($70 new) thermostat ($6 new) from autozone. Buddy came over to do the work with me...
You all know where this is going. We started taking stuff off, P-Steering reservoir, hoses etc, fender skirt trying to get to the water pump on the timing belt (why is this on timing belt???) I had the camera, taking pictures for a DIY post (saw the one for VR6, very naice). We figured out after 5 hours you can't get to the water pump w/out jacking up the engine/trans on the 1.8T either. What is this about? The thermostat is buried just as far in the engine, blocked off by the engine mount. 
Has anybody here ever torn out the 1.8T water pump on their own? I'm trying to track down a factory repair manual, haynes is a huge POS (just take out the water pump and installation is the reverse of removal...). What do you guys suggest on this one? I'm a hardcore DIY'er and don't like this dealership (they also didn't re-attach my skidplate?). 
Any advice welcome (sorry for all the parenthesis







)...


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## kbs3 (Dec 23, 2001)

*Re: Fault Code: P2181-35-00 (Theresias)*

18613/P2181/008577 - Performance Malfunction in Cooling System
Possible Solutions
* Check Engine Coolant Temperature Sender (G62)
* Check Coolant Thermostat
* Check Engine Cooling System
o Put the key on, fan speed on 1, and push the a/c switch. Are both fans kicking on? If not, you found the problem.
o Put the key on and fan speed on 1. Does heat come out readily from the vents?
+ No. Probably the water pump is gone.
+ Yes. Probably the thermostat is gone. 
_____________________________________________________________________________
I am lost. I flip on the a/c and almost always only one fan turns on (smaller one)? 
if i turn on the heat, i get plenty of it...


_Modified by kbs3 at 12:24 AM 5-30-2008_


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## kbs3 (Dec 23, 2001)

*Re: Fault Code: P2181-35-00 (kbs3)*

so from process of elimination I have decided I have a bad thermal switch. My question is, will a bad thermal switch throw the ever condemning P2181 code?
events...
fans run when turning on a/c
jumping the red to the red/white wire fans run
jumping the red to the red/yellow wire fans run
both upper and lower hoses into the radiator are hot
i have the green top sensor


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## Abbruzzesse (May 26, 2004)

*Re: Fault Code: P2181-35-00 (kbs3)*

I'm back: I've taken my 2003 VW Jetta Wagon 1.8T in on account of the MIL/CEL which is on. My car cannot pass inspection with it on. My CEL has been on perpetually for the last 12K miles (I've got 68K right now). 
History with this code: 
23K, ECT Sensor replaced (paid for it)
51K ECT Sensor replaced (paid for it)
52K, p2181 code, but they ran a block test, and everything operating fine
56K, ECT Sensor replaced (under warranty; the 56K is not accurate, I waited to take it in, because I was sick of doing it)
65K, after have the CEL on for awhile, I finally take it in: timing belt needs to be replaced. I talk to my mechanic, who gives a much better price and adds the water pump to the work (he believes VW would throw that in once they got under the hood, and that it's necessary anyways)
68K, take it in for inspection, failed: p2181 code is thrown. 
Took it into the dealer, awaiting word, and the words: "this is on us; we've really fixed this time." They try to charge me a dime and I'm out of there.


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## brian213 (Sep 27, 2007)

Abbruzzesse, you've had a pretty rough time. Best of luck to you.
-Brian


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## meinbug (Jun 26, 2008)

*Re: (brian213)*

2004 NBC, just over 51K miles
My CEL came on last week and I was given the code P2181 by the dealer. Took it to a local VW mechanic as the dealership wanted $635 to replace the Coolant Sensor and Thermostat (ended up paying $145 @ the mechanic).
Car was fine over the weekend, then on my way to work the other day the CEL came back on.







Drove the freeway over the weekend, so it wasn't the first time I was acelerating to 70 mph.
I have it back at the mechanic today, but any thoughts? I've never had an issue with the car before and even though the light is on, I haven't noticed any changes in performance.


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## Abbruzzesse (May 26, 2004)

*Re: Fault Code: P2181-35-00 (Abbruzzesse)*

So, the dealer confirms that the p2181 code goes off, which the dealer tells me means the ECT, Thermostat, Timing Belt and Water Pump are bad. I tell him those have been replaced, and that the ECT has been replaced a couple times. He's says they'll clear the code. HOWEVER, they say that p0231 is going off, the Speed Sensor -- $450. 
I tell them, thanks, but no thanks. Clear the code, please, and I'll look into p0231. Again, my main concern: pass inspection. I take it to my mechanic, and SHOCKER: p2181 is coming up! No p0231. He wants me to fight them, and I want to just pass inspection. BUT, my car can't pass inspection until it goes through a drive cycle, or readiness, without throwing the code. THAT STINKS! 
So, essentially, I need to make sure the code is absolutely clear to pass inspection. 
My mechanic's idea is that it may be a computer error. I don't see anyone, especially those dealing with these repeated MIL problems, discussing this idea. Why not?
Advice? I'm in quite the quandary.


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## Abbruzzesse (May 26, 2004)

*Re: Fault Code: P2181-35-00 (Abbruzzesse)*

What is the warranty on an ECM, by the way? I read on another post elsewhere that the dealer should also test the ECM when p2181 goes off.


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## btenney07 (Jul 11, 2008)

*Re: Fault Code: P2181-35-00 (Abbruzzesse)*

I have a 02 1.8t jetta with 86k miles. The CEL came on, vag-com code p2181 changed coolant temp sensor. One week later CEL came on again with the same code, changed the timing belt, water pump, coolant change, and t stat. All of the parts were ordered from ECS. The code was thrown again this morning on the way to work. At this time I'm all out of ideas and recommendations. thanks.
Brian


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## cycleeric (Feb 4, 2008)

I've got a 02 1.8t Jetta and it's reading the same code P2181 and will not pass inspection. After reading this Im a little concerned that Im looking at a costly repair that will not cure the code.


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## kbs3 (Dec 23, 2001)

*Re: (cycleeric)*

I would be a little Leary about doing allot of work before verifying that your fans are spinning. The sensor is super sensitive. After you get the fan's spinning replace the green top sensor. Sometimes that fixes the problem.


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## scrappy62 (May 21, 2005)

*Re: (kbs3)*

changed out temp sensor, flushed coolant. code came back 300 miles later after resetting battery. I had water pump and timing belt done 40k ago. I'm lost as to where I should go with this next?
Temp gauge reads fine in cluster


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## dana vw tech (Sep 20, 2005)

*Re: (scrappy62)*

Thermostat


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## vwapasionado (Jan 23, 2004)

*Re: (dana vw tech)*

Dana, I came to the same thermostat conclusion on my MKIV R32 with only 25K miles. After EOT sensor, Checking wiring from sensor to ECU and checking the fans being all OK I removed the thermostat. The car never overheated or anything like that but it was setting P2181. While I am waiting for the new one I tested the "failed" thermostat and it seems to operate when I actuate it in boiling water. I do not know how accurately though but it does move. When removing the T-Stat it did not come with the cover, it was stuck up in the housing. I had to gently pry it out with a screw driver. This is quite common isn't it?
Would you know of any test that would condemn the T-Stat for sure. 
I would love to be able to confirm the failure mode. Thanks. http://****************.com/smile/emthup.gif http://****************.com/smile/emthup.gif http://****************.com/smile/emthup.gif


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## tomvw (Feb 9, 2003)

*Re: (vwapasionado)*

the thermostat is the most likely cause, although the water pump should be checked as well.


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## vwapasionado (Jan 23, 2004)

*Re: (tomvw)*

Thank you for your reply Tom. I do not mean to hijack this thread but it has been a very common code in several VW models and the more information the better.
Anyways, I figured that if the T-Stat does not fix it my next stop is the water pump as you stated. Now, if the pump has failed and it is not moving as much volume of coolant as it should; would that cause an overheat fairly quick? I know our cluster does not read real temperature but it is always in the middle. Also, with VAG connected I get 85 to 90 Celsius. 
http://****************.com/smile/emthup.gif


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## brandonfast (Sep 11, 2007)

if vagcom has a obd freeze frame option for the triggering of the cel then use that. in most cases if it triggered the p2181 at 79 degrees its the thermostat sticking open. if it was triggered at like -49 degrees or somthing just not logial then its your temp sensor. easy as that. but i dont know if your vagcom retrieves obd freeze frame data.


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## badmex007 (Aug 23, 2006)

*Re: (brandonfast)*

Hey guys 
I happen to have the same problem but i noticed that my fans don't turn on and my engine needle temp gauge stays in the middle at a reasonable place so i don't thing its the Engine temp. but i tested the fans bridged them to the battery and both turn on. i think it might be the temperate fan switch but i might be wrong i will replace it this week and will get back to you guys.


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## 04silverjetta (Jul 19, 2008)

Man I too have this problem. My temp gauge stays in the middle, the waterpump was replaced 5k mi. ago, fans turn on and the heater works. The only thing was when i opened the coolant tank, there was some smoke/steam coming out of it. also, my car recently crapped out because of overdue oil change making it sluggish. i don't know if it overheated b/c i wasn't there when it happened, but i replaced couple coilpacks and spark plugs and now running fine. any ideas?


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## badmex007 (Aug 23, 2006)

*Re: (badmex007)*

K so i replaced my aux temp sensor and that didn't fix the problem and then i replaced the coolant temp sensor for the ECU reset the ECU and haven't gotten check engine light on. But still the fans don't work they are all getting power and sensors work so does any one have any idea what it could be.


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## Borg-Omen (Jun 15, 2007)

*FV-QR*

I am having the same problem as a couple of the people in here, so i figured i will post as well.
I have the P2181 code , replaced water pump and CTS , still on and car would not heat up , so i replaced the thermostat. A little under a week later the code pops up AGAIN.
I am not really sure where to go from here, my fan turns on when the AC goes on , heat is good. The car will take a longer to get to temp. but still get there. and it will sometimes start getting cooler while driving.
I am thinking i have a bad thermostat







, but i want to make sure before i do it again because it literally has less than 300 miles on it.
What else would cause this , im lost here

*edit* i just remember when i did my thermostat i noticed that the electrical connection (in front of the coolant reservoir, i am not sure that 'switch' that is) was making a really fast clicking noise , whether that is a malfunction (i would assume , but i will leave it to those who know what they are doing to decide







)


_Modified by Borg-Omen at 9:16 AM 3-30-2009_


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## badmex007 (Aug 23, 2006)

*Re: FV-QR (Borg-Omen)*

have you checked the thermo stat sensor or the aux fan switch check those the engine has to be heating up it just can't not be heating up so check those sensor that what i did and erased the codes tell me how th works out.


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## Borg-Omen (Jun 15, 2007)

*FV-QR*

alright.
i will check those out and report back http://****************.com/smile/emthup.gif


_Modified by Borg-Omen at 10:39 AM 3-31-2009_


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## 04silverjetta (Jul 19, 2008)

*Re: FV-QR (Borg-Omen)*

i went to autozone and tried to get a ect sensor and they had two types. green 4 pin and balck 2 pin. which one should i be looking to replace? what does each one do?


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## badmex007 (Aug 23, 2006)

*Re: FV-QR (04silverjetta)*

the 4 pin green one is for the ECU to check it's temperature i'm not exactly sure what the other one does but i have read a lot of info on this and that 4 pin sensor is commonly the problem and go defective out first so try that out. hit me back


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## badmex007 (Aug 23, 2006)

*Re: FV-QR (badmex007)*

yea who ever was asking for the another name for the aux fan sensor just check this site it will help.
http://www.drivewire.com/produ...18030/


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## BlackRabbit0888 (Jun 7, 2005)

*Re: FV-QR (badmex007)*

Badmex007, How/what did you do to test the fan switch faultiness. I'm another one that's been having the dreadful P2181 (for 1.5+ years). Changed out WP, Thermo, and ECT. see this post if interested... http://forums.vwvortex.com/zerothread?id=4339502 
Also, Anyone know how to check if the connection and/or wiring harness is bad, or even know the resistance values for the ECT harness. thx


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## Buckly (Apr 12, 2009)

*Re: FV-QR (BlackRabbit0888)*

I've chased down temp faults before in the past. My rule of thumb is If I diagnose the sensor to be bad (compare actual engine coolant temp with what the ecu thinks, of course checking power, ground and signal.) I will recommend replacing the T-stat. If I find a bad T-stat I insiste on a new temp sensor. Never use an after market temp sensor, it must be VW.
I have found bad grounds to the temp sensor. Or I should say bad grounds in general. The ground is just bad enough that it will start the car, but while cranking the voltage drop in the rest of the system will cause the temp fault. Its always worse on the colder mornings. On start up the ecu uses ECT IAT MAF TPS to calculate air/fuel ratio, coolant temp being one of the more important ones. As well once the ECU goes into fuel control.


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## dr.chop (Apr 8, 2009)

Okay, here's my run at this issue. My wife has a 2004 Jetta wagon with the 2.0l and the CEL has been on for a year+. She never took it in under warranty, so I decided to have it checked myself (should have just bought a vag-com with the $ I wasted). It threw the P2181-035 code on the sheet and another fault number in the instrument/cluster section of 01304 49. 
I am not sure what the later code is, but after reading this thread, the other is common. My question is this: The dealer has said that the "Thermostat was sticking open" causing this code to come up. Not sure how they figured that out just by running the code, but the car has no issues with warming up or overheating. The fans all work as they should, and there are no issues other than the light. Oh, and an occasional stutter when driving on the freeway like a lack of power. The car has 65k on it, so I am confused as to what the problem could be...I am going to change the CTS and I bought a thermostat, but it is a lease going back in October and don't want to waste a dime on it. Any insight?


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## ThatJustHappened (Nov 2, 2007)

i just got the p2181 with autozone device. i took the car to carmax and they said it was the catalytic converter thats bad. im not sure who to believe now. also, where is the thermostar in car???


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## trouble1mk (Sep 25, 2005)

*Re: (ThatJustHappened)*


_Quote, originally posted by *ThatJustHappened* »_i just got the p2181 with autozone device. i took the car to carmax and they said it was the catalytic converter thats bad. im not sure who to believe now. also, where is the thermostar in car??? 

P2181 usually is a intermittly stuck thermostate. or bad connection on the ect wiring.


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## vw lifer (Jun 24, 2007)

*Re: (vwapasionado)*

Usually the malfunction in the cooling system code is caused by a faulty ECT sensor. Other than the sensor, the cooling system is not really monitored by the ecm.
The ECT sensor is sensitive, so if you are running anything other than Pentosin or VW pink coolant I would recommend flushing the system and replacing the coolant. If you have ever put other coolant in the system than the above 2 listed, then you might have issues until the system is purged. Other coolants will goop up the system and can even gel up.
Water pump impellers are made of phenolic plastic and will eventually heat fatigue and fall apart. Just go ahead and plan on replacing them every time you get the timing belt replaced. It is a wear and tear item on the newer VWs, kind of like brake pads.


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## vw lifer (Jun 24, 2007)

*Re: (vw lifer)*

Also, replace the coolant atleast every 40k miles ideally on VW engines.
Timing belts should really be replaced about every 60k miles to avoid breaking and bending valves. I've seen too many break before 100k miles to recommend that change interval.


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## manlee (Jul 6, 2008)

*Re: ECT*

I have an '03 with 51.5k miles. I just got that p2181 CEL. I bought the car used, should the dealer take car of my ECT for me? or is that not covered under the original warranty?
Otherwise, I will try that green 4 pin thingy from autozone. My friend has an ecu chip reader, and I used it to clear the CEL sensor.
I don't mind the DIY route, but if the dealer will cover it, i'll have them take care of it!
So far my temp gauge sits around 190 when i'm driving and doesn't overheat, although i think the floorboard area does get a little warm (could be because it's warming up outside though).
Car seems to run fine without any issues.
Thanks for your thoughts.



_Modified by manlee at 1:45 PM 5-11-2009_


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## guanatozridez (Jan 8, 2008)

i hav an 04 GLI and just got CEL n P2181. It has 42,600 miles and recently replaced the coolant temp sensor, coilpacks, and MAF. Do u guys think I should replace the timing belt, water pump n thermostat? And will this fix the problem? Any suggestions or thoughts. BTW the car is chipped with intake and turbo back exhaust.


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## regahsof (Jul 25, 2009)

*Re: (guanatozridez)*

2003 Jetta 2.0 liter, have owned car for 4 months, most of time with CEL light on. (Last month I drove to the Badlands and back no problem.) When the light first came on, maybe in April, I had the codes pulled: P2181 and P0420 (cat. con.).
Last week I failed Illinois' emissions test on account of the P2181 code (though interestingly the test site didn't note the P0420 code). This week I took the car in to a local auto repair shop (not VW specialists) to assist with fixing. They did diagnosis and recommended replacing thermostat (opening too early), which I just had them do today ($314, incl. diagnostic charge). Light is off now, but they wouldn't sign off for me to re-test for emissions because I guess they need a week or so for "readying"? or what I read on here as a "drive cycle"(?).
If the light remains off after seven days (everyone's hope), I take it back to them and hopefully all is good. If the light comes on, our verbal agreement was for me to take the car to the dealer to deal with the P0420 cat. con. code, which they also pulled, which this shop can't deal with. This, of course, is assuming the light comes on because of the P0420 code and not the P2181 code (!). 
I hope all goes well, which I guess means that the light won't come on, they complete the paperwork, and I pass the emissions re-test.
I decided to drive to the VW dealer just after this and run by them what this shop did. In a quick chat as the mechanics were picking up their checks, the service manager pointed out a couple things: why didn't this shop also replace the coolant temperature sensor (CTS) since they were in the thermostat area? Why didn't this shop fill out the paperwork and send me right away to re-test since they technically cleared the code for the P2181 fault that the testing site pulled? Both these things sound slightly fishy to him. I'll have to wait a week and see what the story is...
I'll keep you all posted! I guess the worst case scenario is that the light comes back on, and the P2181 code is still there!
P.S. The VW service manager I spoke with about the catalytic converter code says that this code (P0420) is often a symptom of the cooling system issues. VW can replace the cat. con. under warranty (up to 100k, or was it extended?) provided that the catalytic converter code is the ONLY one up.


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## regahsof (Jul 25, 2009)

*Re: (regahsof)*

Yup, the thermostat cured it! No more Check Engine Light. I passed emissions. Yay!


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## Dipstick (Sep 17, 2009)

*Re: FV-QR (Buckly)*

"never use an aftermarket temp sensor"...Have you seen issues with those? I put in an O'Reilly's green sensor and the CEL went out for several days, but came back. Code P2181-35-00, and 01039. Also gives "30-10 Open or short to plus - intermittent".
Thanks
04 VW Beetle 2.0L


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## steinosaur (Oct 15, 2009)

*Re: FV-QR (Dipstick)*

So i've been looking through this thread a lot of good stuff, as i have thrown this code also. The guy before me had the coolant temp sensor replaced, im gonna pull it and make sure its the green top. Car runs fine, just pops this code up, i erased it first time it came, now it came back about 1000 miles later. AC/Fans/ And Heat work. Is there a diy on checking the wiring, and whats this ECS im reading about, wheres that located and is that a common fix?
Thanks


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## strykr24 (Jan 31, 2010)

*Re: (Uwe)*

Ok so yesterday my car (2003 Jetta GL 2.0) kicked a P2181, I cleared it and drove another 20 some miles to see if it reset it, and it hasn't come back on yet. I just went out and checked, I have the green top sensor, my fans both come on when I turn on AC, and I get plenty of heat when I turn the heater on. Car operating temp hits 190 and stays there, like normal.

Side note, my key fob is also having a very reduced range, and it is no longer unlocking the entire car, just the driver door. Any ideas what could be causing this? And any help with the 2181 is greatly appreciated.


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## hbmom (Aug 10, 2010)

dr.chop said:


> Okay, here's my run at this issue. My wife has a 2004 Jetta wagon with the 2.0l and the CEL has been on for a year+. She never took it in under warranty, so I decided to have it checked myself (should have just bought a vag-com with the $ I wasted). It threw the P2181-035 code on the sheet and another fault number in the instrument/cluster section of 01304 49.
> I am not sure what the later code is, but after reading this thread, the other is common. My question is this: The dealer has said that the "Thermostat was sticking open" causing this code to come up. Not sure how they figured that out just by running the code, but the car has no issues with warming up or overheating. The fans all work as they should, and there are no issues other than the light. Oh, and an occasional stutter when driving on the freeway like a lack of power. The car has 65k on it, so I am confused as to what the problem could be...I am going to change the CTS and I bought a thermostat, but it is a lease going back in October and don't want to waste a dime on it. Any insight?


 
I have the EXACT same problem, same car, same year, same mileage, same code, same stutter. The CTS was replaced and everything else was confirmed fine by VW. Did you ever get a conclusive answer?


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## BGTI1 (Sep 2, 2002)

All right here is my take on this issue. the car is a 2004 VW Jetta Wagon 2.0 with 73K miles
I replaced the CTS for the 3rd time on the car and the CEL came back within 40 miles with the same P2181 code. This time I said enough and I went out and got the VCDS from Ross-tech for $370 and read everything I could about this issue. So here is how I approached this issue: 
1) Changed the timing belt, tensioner and water pump cuz it was about time.
2) Changed the thermostat and coolant.
3) Changed the battery
3) Check the fans and found out that the main fan (driver side) is not working at all. The passenger fan (smaller one) was working on just one speed. I checked the fans by bypassing the radiator fan switch on the driver side of the radiator. Just bridge the terminals and look for the fans to spin. There are 2 speeds so check both. 
Checked the fan fuses and they were ok so then I applied battery power straight to the fans. The fans connectors are on the bottom driver side of the radiator. So far I found out that the main fan is not working at all and that the smaller fan is working on both speeds. So now I got to replace the main fan and the fan controller cuz the small fan was working on only one speed when I bypassed the fan switch. 

So make sure that the fan work properly both speeds and that the radiator fan switch is also working properly. If they don't work then the car can throw the P2181 code. 
The weird thing is that the car is not overheating or anything and I am pretty sure they have not been working for a while because my dad has been driving the car with the CEL on for about a year. 
So I cleared the code and i will be taking the car on a short trip tomorrow to see if the CEL comes back on. If it does not the I will take it in for smog. And then next week I will change the fan and controller and see what happens. 

Oh yeah I also applied some di-electric grease on the CTS connector to make sure it always make connection. You can get that from an electronics store. 

I will keep you guys updated on how it goes.


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## justwatson (Mar 31, 2010)

*same issues!*

Hey i am having similar issues with my 2003 GTI 1.8T. My car seems to be running a little rough and my gas mileage has seemed to decrease a little. I got the same code of P2181 ( cooling system performance). for some reason though i am suspicious to think that it might be a mass air flow leak because about a couple months ago i had a check engine light for the mass air flow leak and then i reset the ECU, no this light came on and i think that it has something to do with it. Did you ever figure out what the problem was?


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## trola04 (Feb 10, 2011)

*Jetta 1.8t Thermostat*

If you never overheat and you've got a green ECT sensor then it is likely the thermostat. 

To test this theory drive up the biggest hill around your city preferably a highway hill. Then coast down the hill in gear at a decent speed, and watch your temperature, if temp drops even a bit your thermostat is either stuck open/no able to close all the way/or opening at too low of a temperature. 

The stock thermostat does not have a "jiggle valve", a new OEM replacement should. This feature allows a small amount of coolant to bypass the thermostat so that it is subject to the coolant temperature on both sides. Without this "jiggle valve" the cold side of the thermostat affects its ability to operate in the true ambient coolant temperature. This jiggle valve should be used when replacing a thermostat, if your parts dealer does not have one with such a feature then he/she has old stock.

Good Luck.


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## vwemporium (May 27, 2002)

Here is your solution.

::::: WARNING EMERGENCY FORUM ACTION MESSAGE:::::

THIS POST VACATED BY JACK TO PROTECT CONTENT FROM FALLING INTO THE GAPING HOLE OF THE VORTEX! 

THIS SOLAR SYSTEM IS IN DANGER OF A BLACK-HOLE!
YOU TO CAN ESCAPE!
I CAN BE FOUND VIA THIS DHD STAR-GATE ADDRESS......
http://forums.ross-tech.com/member.p...European_Parts


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## knonukes (Mar 5, 2011)

*To the Inquirers of the code p2181*

My CEL Dash light popped on. After scanning for codes, I discovered it was due to a p2181. Originally, I believed it was due to a sticking thermostat. After researching this website, I decided it also could have been due to the ECT sensor. Therefore, I replaced the inexpensive ECT sensor which I originally had the black sensor and the bought the upgraded green sensor, reset the code. Then after driving for a couple of days, the CEL popped back on. Therefore, I was certain my original presumption was correct. Therefore, I changed my thermostat and the CEL light has not popped back on. Thanks for your incites!


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## jaima1000 (Apr 7, 2011)

*fixed it*

This thermostat listed by the Poster above did work on fixing my long standing P2181 error code.. !!!

http://cgi.ebay.com/ebaymotors/VW-AU...Q5fAccessories

BTW, I am not too knowledgeable on cars and not quite sure why this thermostat fixed it. I would be curious to know why it worked. As far as my car goes there never was any visible problem I could see, It never ran hot or had any problems except the stupid check engine light with this elusive code attached.


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## robbielozier (May 29, 2011)

*p2181 code*

KBS3 SAID Put the key on, fan speed on 1, and push the a/c switch. Are both fans kicking on? If not, you found the problem.

When I do this only one fan kicks on? Any suggestions on where I should start? 

I have a 2003 VW Jetta GL


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## [email protected] Parts (Nov 27, 2006)

Yup

Trace the wiring and verify, fuses, grounds, the fan and module.

When playing here, post a auto-scan.

I have the modules and fans in stock just let me know what # you need or email me your scan so I can tell most of the time from that.

We even have some used fans in some cases on ebay store.

Best,


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## gliphil (Apr 5, 2010)

*2181*

I also have had the dreaded code. I have chased it for a while. But I thought nothing of it when I bent my valves after neglecting my timing belt. But after I replaced my head my car has not over heated (according to my guage). But I did go under my hood the second I got the code and notice that in my resivoire I seen the coolant boiling. I have changed my ect sensor with an az one before cause I was desparate and vw was closed. But I will try the factory ect sensor and factory thermostat and will post any improvements.


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## gliphil (Apr 5, 2010)

So it was a pain in the &$$ to do the thermostat cause its behind the alternator but with some fresh g12 coolant I did it. I almost want to say that my car idles better. I drove about 30 miles today and no codes or any thing. I will keep you guys posted to let you know if anything changes


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## maldorer (Jan 18, 2009)

*I've been ignoring this code for 5 years*

Have a 2003 1.8T Jetta. First time CEL appeared I bought a code reader ($60) and followed its advice and checked coolant, replaced ECT, then after code again, replaced T Stat. A few weeks later, CEL again. Check code: 2181, erase. A few months later, CEL, erase, again CEL in a couple weeks, erase. Meanwhile, car never drives wrong or overheats or AC not work or heat not work. I think this is software problem in the ECU. I'll ignore it until I see smoke or the car doesn't work.


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## [email protected] Parts (Nov 27, 2006)

:::::ALERT FORUM ACTION EMERGENCY MESSAGE:::::

THIS POST MOVED/VACATED BY JACK TO PROTECT CONTENT FALLING INTO THE GAPING HOLE OF THE VORTEX

IT SEEMS NO GOOD DEED GOES UNPUNISHED!

http://www.youtube.com/watch?v=HaoySOGlZ_U 

Just email or PM John [email protected] as to why I have chosen to do this for a modification answer to these posts.....
Ultimately this is his fault for how the account was handled.
[email protected]
You could say I feel insulted and abused..........


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## mwebb (Apr 19, 2008)

*non OEM parts do not work*

p2081 is a time to temp or coolant MAP DTC 
very often set by dogshnit made in china parts sold by AutoJunk and other places similar . 

with VCDS on many but not all VW and Audi systems you can use the OBD2 function , select 
MODE 6 
TID $09 is the time to temp test , there is a MIN or a MAX value and a TEST value 
the TEST value may equal to but never exceed a MAX value and may equal but never be less than a MIN value 

if the TEST value exceeds a MAX value or is less than a MIN value ,
begin by replacing the thermostat AND the Coolant temp sensor with OEM VW or AUDI parts , many of the later thermostats are active thermostats under control of the ECM .
do not use FRED's parts , ever . 

the test results are also available in advanced measuring Blocks , just scroll and search for them , you will find many additional things you never knew were there


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## [email protected] Parts (Nov 27, 2006)

:::::ALERT FORUM ACTION EMERGENCY MESSAGE:::::

THIS POST MOVED/VACATED BY JACK TO PROTECT CONTENT FALLING INTO THE GAPING HOLE OF THE VORTEX

IT SEEMS NO GOOD DEED GOES UNPUNISHED!

http://www.youtube.com/watch?v=HaoySOGlZ_U 

Just email or PM John [email protected] as to why I have chosen to do this for a modification answer to these posts.....
Ultimately this is his fault for how the account was handled.
[email protected]
You could say I feel insulted and abused..........


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## gliphil (Apr 5, 2010)

So im at 1000 miles since my last post and I still have not got any codes. I replaced my t-stat ect and g12 coolant all from vw. T-stat was $35 ect was $45my and coolant was $20. At the dealer. I did it my self and took altogether about an hour. The easiest way to get to the t-stat is to remove the alternator. Although it is possible to get to it with out removing it. But you need a 10mm wrench


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## Kam3152 (Mar 17, 2013)

*P2181 help!*

RE: 2004 VW Jetta 2.0 
.................................... 
Hello guys 
I am new to this thread and do not know a lot about cars. All I know is what I've been forced to learn from trying to fix this awful p2181 code.... 

I found it interesting that so many of us have this same incurable code. I got an interesting diagnosis today, one that I have not read in anyone else's posts. Please tell me what you think. I'm a little skeptical.... 

But first, here's my cars back story: 

I have been living with p2181 for 3+ years now... My CEL light came on randomly one day and I just cleared the code hoping it was a mistake. A few days later the code came up again. After doing some googling,I decided to replace my CTS from O'riley auto parts ($10). A day later the CEL and code came back... 
The dash gauge has alway (and still does read a stable 190 degrees... ) I decided to investigate. I hooked up my OBDCOM reader via my laptop and drove around a bit. I could read the actual temperature from the OBDCOM coming in around 220degrees. I assume this high temp is what is causing the error code and CEL to come on? I turned on my heater full blast ( all the way red/hot & 4 fan speed). I could see the temp immediately drop down to normal range. I had a smog inspection coming up so I cleared the code and drove around with my laptop to monitor the actual temp and view the drive cycle process. (You will fail smog inspection with this code & an incomplete drive cycle). In order to complete the drive cycle and not re-trigger the p2181 CEL, you need to drive the entire time with the heater ON! I did this and passed easily. I recently took the car into a mechanic to have the thermostat replaced thinking that this was the next most probable cause. The mechanic did a series of tests to make sure it was the thermostat before replacing it. He tested the CTS with his instruments and that came back fine. He tested the fans, they were in working order, they took out and tested the thermostat and it seemed to be functioning properly ( hmm...) they also checked the coolant and it seemed to be fine. Annoying. Their final diagnosis was that my ECU (computer) has a bad "relay" that fails to initiate the "engine cooling system". 

Now to all you who know VWs, is this a probable cause for this error code. 
It seems like almost everyone is saying to replace the temp sensor and then the thermostat, but then again, there are a lot of people on here that say they have replaced those parts and are still getting the p2181.... 

I need help. If anyone has any good advice, please HELP 
Thanks


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## [email protected] Parts (Nov 27, 2006)

.:::::ALERT FORUM ACTION EMERGENCY MESSAGE::::: 

THIS POST MOVED/VACATED BY JACK TO PROTECT CONTENT FALLING INTO THE GAPING HOLE OF THE VORTEX 

IT SEEMS NO GOOD DEED GOES UNPUNISHED! 

http://www.youtube.com/watch?v=HaoySOGlZ_U 

Just email or PM John [email protected] as to why I have chosen to do this for a modification answer to these posts..... 
Ultimately this is his fault for how the account was handled. 
[email protected] 
You could say I feel insulted and abused..........


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## Kam3152 (Mar 17, 2013)

*Thank you*

Thank you so much for the information. I will give that a try and report back 
And sorry I'm such a n00b 
-k


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## Bickot (Jun 20, 2013)

I drive an 03 jetta 1.8t n had the same code come up reading the reviews I just left it alone, I recently hit a raccoon and had to replace my radiator and shortly after the light went off


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## pavel1968 (Mar 18, 2014)

*p2181 code*

ihad my epc light come on with p2181 code but also p2181, p0321 and p0172. it's a 2003 vw golf 2.0. this just happened a couple of days ago. when the car sits for a long period and i go to start it it fires right up. if its only been sitting for little while i have to turn it over several times to get it to start. when i'm driving it occasionally misses. before the epc light i was geting the p0102 fault with an engine light on. i recently replaced maf sensor and last year replaced o2 sensors and spark plugs. p0102 code came back as well? anyone with some insight?


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## [email protected] Parts (Nov 27, 2006)

This is not an auto-scan......


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## mul21100 (Jan 10, 2015)

*P-2181 Sensor*

I have a 2009 Jetta GLI and the P-2181 code came up 2 weeks ago with the check engine light. I took it in to the dealer and they said it's the thermostat on the water pump. However the water pump and thermostat are attached together so I would need to replace the whole assembly. Expensive to say the least. Now the check engine light has gone off on it's own. Does that mean that I don't have a problem? I'm wondering if I should still replace the water pump or wait and see? I've seen no overheating.


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