# 2003 GTI 1.8T : P0237 and P0171



## bizurk (Jan 29, 2010)

OBD fault codes:
P0237 turbo/sc booster sensor a ckt low
P0171 System Too Lean (Bank 1)
Ive searched these forums and googled quite a bit... Can't really find a sound solution. WARNING: I've had this car for about a week... I'm a small block chevy guy venturing into a whole new world. And so far I like it quite a bit. If you need more information to diagnose please just tell me what you need to know, and be as specific as possible ( Because i probably wont know what youre talking about and ill have to do research to figure it out ) Anyways, I got 60 days, so hopefully I can get this figured out. Thanks guys! =]


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## bizurk (Jan 29, 2010)

*Re: 2003 GTI 1.8T : P0237 and P0171 (bizurk)*

Bump...

Please guys, any information is helpful. So far from my research I've found i shold change my Mass Airflow Filter. And then move onto the 4 O2 sensors.


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## cwcabrio (Dec 16, 2009)

*Re: 2003 GTI 1.8T : P0237 and P0171 (bizurk)*

Welcome to vw.

_Quote, originally posted by *bizurk* »_P0237 turbo/sc booster sensor a ckt low

For this one you'll have to check the wiring and conector for the sensor (more likely some dirt on the conector) and last check the sensor.

_Quote, originally posted by *bizurk* »_P0171 System Too Lean (Bank 1)

Check for a clean air filter, vacuum leaks and MAF first. Could be fuel pressure, o2 sensors (2 of them), fuel injectors, EVAP valves, SAI system.
If you intend to do the work yourself I recomend a good book like Bentley and a good scanner.
Good luck and keep posting.


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## bizurk (Jan 29, 2010)

*Re: 2003 GTI 1.8T : P0237 and P0171 (cwcabrio)*

What would a good scanner be called? OBDII? Ill check everything else out as well. Thank you for taking the time to respond!


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## 01TornadoWolf (Jun 18, 2009)

*Re: 2003 GTI 1.8T : P0237 and P0171 (bizurk)*

http://www.ross-tech.com/


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## bizurk (Jan 29, 2010)

So im looking around my engine compartment, and I see something pretty messed up... The boost gage is tapping into the vacuum line, and it looks like a real half ass job. Theres maybe 10 zip ties holding this thing together... If this was leaking.. could it cause the engine to throw the check engine and these codes? Ill post pictures later.


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## bizurk (Jan 29, 2010)

**UPDATE**
So I've replaced the Mass Airflow Filter and after 50 miles the check engine light is back and ready for more. So im just going to go to OREILEY Autoparts and buy one of those scanners for 160$. Scan it, and see if the codes have changed at all.


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## cwcabrio (Dec 16, 2009)

*Re: (bizurk)*

All right keep posting.
By the way how's the ride runnin'?
What was the outcome of the vacuum job?


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## bizurk (Jan 29, 2010)

*Re: (cwcabrio)*

Do I have to get a scanner from rosstech? They have them here http://www.oreillyauto.com/sit...C0103 Will this work? Seems like the rosstech ones are like 300$... Plus my laptop is a mac, so i would have to dualboot windows which wouldn't be TO big of a pain, but yeah.
And to cwcabrio:
The car runs absolutely great. if that little light wasent on you would never know anything was wrong with the car ( Which is how i got screwed into buying it =D ) I haven't had time to do the vacuum thing yet, its been raining and my job has been keeping me much to late. ( New girlfriend as well =] ) I also need to clean my K&N filter, because its all dirty. Not enough hours in the day!


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## cwcabrio (Dec 16, 2009)

*Re: (bizurk)*

The rosstech scanner is the best out there, but any obd2 scanner will give you the basic codes, and there are some that would give you the brand specific codes.
So you don't have to get the rosstech unless you plan to keep your vw for a long time, plan to work yourself on it and can afford it.
Good to hear is runnin' great. But I suggest gettin the vacuum job done soon, I think there is where your gettin the extra unmeassured air that is leanning your mixture, and hot runnin engines tend to be expensive repairs on the long run.
Good luck and keep posting.


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## bizurk (Jan 29, 2010)

Yeah so the rosstech websites leaves something to be desired ( Im a web developer ) so im still a bit confused on which one i need exactly...
And the vacuum leak will cause my engine to run hot?


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## VWJettaCarat (Apr 8, 2004)

*Re: (bizurk)*

http://wiki.ross-tech.com/inde...00567
This sensor is located on top of the Intercooler, make sure it's plugged in(as someone else mentioned) and that the connections are not corroded. if all Checks out, follow the wiring to make sure there are no broken/cut or cracked wires, check the MA*P* sensor.
http://wiki.ross-tech.com/inde...00369
You already replaced the MA*F* sensor.
Here's a diagram to help you out











_Modified by VWJettaCarat at 3:55 PM 2-10-2010_


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## bizurk (Jan 29, 2010)

*Re: (VWJettaCarat)*


_Quote, originally posted by *VWJettaCarat* »_http://wiki.ross-tech.com/inde...00567
This sensor is located on top of the Intercooler, make sure it's plugged in(as someone else mentioned) and that the connections are not corroded. if all Checks out, follow the wiring to make sure there are no broken/cut or cracked wires, check the MA*P* sensor.


Ok so i found this sensor, and unplugged it to take a look. The actual plug looks pretty messed up (Cracked plastic ) So next I should replace the plug and the actual sensor correct?
I also found a few plugs with no where to go behind the passenger headlight (Next to where the windshield wiper fluid is)
Thank you very much for the diagram!
**UPDATE**
Wow so i just realized the MAP and the Boost Sensor are the same part... im an idiot... SO anyway i took another look in the engine compartment for fun at work... And found 3 loose plugs. 2 of them pluged into each other, and the third turned out to be the highbeam plug with no blub in it.








_Modified by bizurk at 3:43 PM 2-10-2010_ 


_Modified by bizurk at 7:55 PM 2-10-2010_


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## bizurk (Jan 29, 2010)

*Re: (bizurk)*

























So here i am, with another update. I took my car to Pepboys today and got a free error code scan. And guess what! The error code "P0237 turbo/sc booster sensor a ckt low" is now gone! So apparently the new MAF did the trick for that problem. The only problem that remains it the "P0171 System Too Lean (Bank 1)" Which i have a hunch on. In the photos above, you can see where the boost gauge is T'd off for a reading. Its safe to say its totally half ass. If this was leaking, would that be the cause of the "P0171 System Too Lean (Bank 1)" reading?








I also posted a photo of the plug that I found that was unplugged, does anyone recognize what that plug is for? Thanks in advance and let me know if i need anymore photos.


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## cwcabrio (Dec 16, 2009)

*Re: (bizurk)*

Nice job bizurk, you got one fix already.
For the 'system too lean' I would start by fixing that mess of a vac boost gauge install. Seem to me like the blue hose is bent and keeping the fuel pressure regulator from working correctly.
By the way, when the engine gets unmeasured air (like from vac leaks), the air fuel mixture gets lean, thats too much air in the mix causing more heat from the combustion, making the cooling system work harder to remove the heat.
Not sure what the plug you found is for, just follow the wires and you'll see, or post a pic of it and we'll tell you.
Good luck and keep posting.


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## bizurk (Jan 29, 2010)

*Re: (cwcabrio)*


_Quote, originally posted by *cwcabrio* »_
Not sure what the plug you found is for, just follow the wires and you'll see, or post a pic of it and we'll tell you.
Good luck and keep posting.

The plug im talking about is in the third picture. 
Ill probably just go ahead and remove my boost gage for now to see if that gets rid of the code. I have to disconnect the battery after the fix correct? Sorry guys, this is the newest car ive ever had. Im used to a 1959 Belair and a 1963 Chevy C10. So the computers in cars is foreign to me =]


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## cwcabrio (Dec 16, 2009)

*Re: (bizurk)*

I mean a pic of the thing that the wire attaches to... haha
Not sure if unpluggin the bat erases the codes though. I use a scaner.


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## bizurk (Jan 29, 2010)

*Re: (cwcabrio)*


_Quote, originally posted by *cwcabrio* »_I mean a pic of the thing that the wire attaches to... haha
Not sure if unpluggin the bat erases the codes though. I use a scaner.

I need some advice on which scanner to get for my car... Anyone wanna link me?


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## bizurk (Jan 29, 2010)

Anyone with advice on the scanner?


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## bizurk (Jan 29, 2010)

So i have fixed the boost gage vacuume line problem, and the light still persists to stay on. Where should i move onto next to fix the "P0171 System Too Lean (Bank 1)" Code??


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## 1.8Tjettta01 (Nov 12, 2007)

system too lean is a Vacuum leak. you should check those rubber black lines for oil around them. 
it could be under the manifold too. grab a bright flashlight
replace your MAF which is a great idea.
Replace the spark plugs which is a good idea.
If you have emissions coming up in CA, just unplug the battery than go get tested at best.


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## bizurk (Jan 29, 2010)

*Re: (1.8Tjettta01)*


_Quote, originally posted by *1.8Tjettta01* »_system too lean is a Vacuum leak. you should check those rubber black lines for oil around them.

which black rubber hoses?? There whole engine is filled with rubber hoses. :/ 
I've already replaced the MAF, but have yet to get new plugs. I'll be sure to do that this weekend... Anyway I've done the battery trick, and I'm sitting in the waiting room to see if it passes or not. Cross your fingers :/


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## 1.8Tjettta01 (Nov 12, 2007)

ah ok, your a stock man. I will show you when i get the chance. a video showing where the possible boost leaks are. I don't live anywhere near carlsbad in CA so i was hope i could help you. oh well, here is a link below where the Major boost leak comes from.
http://forums.vwvortex.com/zerothread?id=4778652


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## bizurk (Jan 29, 2010)

*Re: (1.8Tjettta01)*


_Quote, originally posted by *1.8Tjettta01* »_ah ok, your a stock man. I will show you when i get the chance. a video showing where the possible boost leaks are. I don't live anywhere near carlsbad in CA so i was hope i could help you. oh well, here is a link below where the Major boost leak comes from.
http://forums.vwvortex.com/zerothread?id=4778652

Wow i have the same exact problem.... same break and everything... It was up against it still so i couldnt tell it was broken without wiggleing it :/
Also, i found another huge problem. My K&N airfilter is clamped directly to my MAF... so im missing the fitting that some vaumme hose is suppose to attach to. Its about an inch in diameter.. SO now i need to find a stock air box or get something else that will work... Does Eurojet have something like this? Id like to just order everything in one. :/
BTW without all your help i would be totally ****ed. So thank you all for taking the time to post in this thread. Ill try my best to someday return the favor.


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## 1.8Tjettta01 (Nov 12, 2007)

Oh you mean that hose that connected to the stock air box? Just go to pepboys or anything where else and buy a tiny Filter. than zip it on.
thats called the SAI hose. secondary air intake hose. If that lil thing doesn't havea filter on it, it could be 1 cause why you are running lean.


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## 01golfavh (May 27, 2011)

*EGR? Engine Bay diagram?*

Hello,
Where is the EGR/ valve located on a 2001 golf 2.0L AVH non turbo? Does anyone have a well illustrated engine diagram stating practically every sensor and important part on this car more descriptive than a haynes manual?


Thanks


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## BassNotes (Mar 16, 2005)

VCDS from Ross-Tech is my recommendation.


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## forcefedjetta (Aug 14, 2003)

Where u located in guessing not near me I'm in mass if ur close I could help out


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