# help with stubborn MIL :(



## ~clover (May 18, 2014)

Hoping someone here might be able to help. My sister has a 2009 Jetta 2.5 that she got about a year and a half ago. Ever since she got it, it's been having check engine light issues intermittently. We've had it at the dealer multiple times for them to fix the car, and every couple months the issues just come back again. The first time the car was brought in was Oct. 2012 (about a month after the car was bought) and the dealer scanned the codes and found faults for Oxygen sensor Bank 1 Sensor 2. They replaced the O2 sensor and the code went away. In May 2013 the MIL came back on. The dealer scanned the code and got P0140 (Oxygen sensor no activity detected, bank 1 sensor 2), P2096 (Post catalyst fuel trim system too lean), and P2270 (oxygen sensor signal stuck lean bank 1 sensor 2). They replaced the rear oxygen sensor again. MIL went away for a few more months. Sept. 2013 the MIL came back on again. This time they had P2096, P0140, and P2270. They replaced the alternator, ECM, and front oxygen sensor. Light went away again for a few more months and came back in February of this year. The MIL was on and the car wouldn't accelerate hard (it literally felt like it was in limp mode) and was blowing white smoke. We decided to try a different dealer and took it to them and the dealer scanned the codes and found the knock sensor was faulty and replaced that. That brings us to today... today the MIL came on again. I just scanned it and it has codes p0141 (o2 heater circuit bank 1 sensor 2), p2097 (Post catalyst fuel trim ratio too rich bank 1), and p2270 (o2 sensor signal stuck bank 1 sensor 2). We'll take it to VW again since it's under warranty still. The car was bought certified used in late septemberish of 2012. The certified warranty is about to run out around september/october of this year. We really want to get the car fixed for good before the warranty expires, because once it does it will probably cost a ton of money to have VW trying to fix the issues and throwing parts at it hoping to fix the problem. Does anyone here have any ideas what could be the problem and what to look for? She loves the car but having the same issue pop up every couple months is inconvenient and frustrating.


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## le0n (Jun 12, 2013)

I typed them this way so it's not so confusing:

Oct 2012
*Faults for O2 Sensor B1, S2*
Replaced Rear O2 sensor

May 2013
*P0140 - (Oxygen sensor no activity detected, bank 1 sensor 2)*
*P2096 - (Post catalyst fuel trim system too lean)*
*P2270 - (oxygen sensor signal stuck lean bank 1 sensor 2)*
Replaced Rear O2 sensor

Sep 2013
*P0140 - (Oxygen sensor no activity detected, bank 1 sensor 2)*
*P2096 - (Post catalyst fuel trim system too lean)*
*P2270 - (oxygen sensor signal stuck lean bank 1 sensor 2)*
Replaced Alternator
Replaced ECM
Replaced Front O2 Sensor

Feb 2014
Knock Sensor Code
Replaced Knock Sensor

May 2014
*P0141 - (o2 heater circuit bank 1 sensor 2)*
*P2097 - (Post catalyst fuel trim ratio too rich bank 1)*
*P2270 - (o2 sensor signal stuck bank 1 sensor 2)*

Aside from the failed knock sensor, has the car run fine, or at least seemingly ran fine? Good power, good mpgs, easy starts, no exhaust smoke, etc.

I would have swapped the harness for the rear O2 sensor.

How many miles are on the vehicle? There is a federal emissions warranty on our vehicles. If it is less than 80k miles, most emission components are covered.


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## ~clover (May 18, 2014)

le0n said:


> I typed them this way so it's not so confusing:
> 
> Oct 2012
> *Faults for O2 Sensor B1, S2*
> ...


Thanks I appreciate it, that is much easier to see! The car has just under 45k miles. It's seems to run fine even with the codes. The only one that had it running rough was when the knock sensor went bad. 
Dropped it off at the dealer this morning and still waiting to hear back about it. I just hope they can get it fixed for good before the warranty runs out.
If anyone has any ideas or suggestions please chime in... I don't know if the dealer just doesn't know what they're doing, or if the problem is just really that wacky


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## le0n (Jun 12, 2013)

~clover said:


> The car has just under 45k miles. It's seems to run fine even with the codes. The only one that had it running rough was when the knock sensor went bad.


wow. too low in mileage to be having anything weird happening.

that's a good sign that it runs properly.

a bad knock sensor will be very evident and would need to be replaced.

however, i have no idea why they would have replaced the following:

Replaced Alternator
Replaced ECM
Replaced Front O2 Sensor
^^ they got the rear o2 sensor codes and decided to replace other components not related to the codes 

they should have been checking for poor grounding and bad wire harness to the o2 sensors. unless your sister is off-roading, she shouldn't be getting having these repeated issues. the first instance could have been a bad sensor, the next instances should have made them suspect to the wiring.

if you haven't replaced your battery within the past year, have them test your battery please. wacky stuff can happen when our batteries get below a certain threshold.


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## ~clover (May 18, 2014)

le0n said:


> wow. too low in mileage to be having anything weird happening.
> 
> that's a good sign that it runs properly.
> 
> ...


Thanks for the advice. I'll def have the battery checked. and she doesn't do any offroading.. she literally drives the car maybe 4 miles to work and back each day and that's about it. I don't know why they replaced the alternator, ecm and o2 sensor. I know the dealer was stumped and had some VW tech "specialist" come in from NJ come in to take a look at it (this was at the first dealer). I kinda think the first dealer might not know what they're doing which is why we're trying another dealer this time. Hopefully they'll have an update soon and be able to fix it. Is there any way I could check the wiring harness myself? I know enough about cars to do the basic stuff... oil change, tire roatation, I've swapped out suspension systems before and stuff. Just never done electrical stuff and didn't want to mess with this car since it's still under warranty.


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## le0n (Jun 12, 2013)

that's good that it's at a different dealership now.

this problem shouldn't be hard to resolve, you just have to have the right technician diagnose it.

if you have vagcom you can scan the activity for those components to see if they're working properly. if they are working properly, you can move around the harness to see if any readings are interrupted (to test for intermittent short)

you can also check to see if any fuses are being blown. 

honestly, let the new tech handle it.

keep us updated if you don't mind.


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## ~clover (May 18, 2014)

le0n said:


> that's good that it's at a different dealership now.
> 
> this problem shouldn't be hard to resolve, you just have to have the right technician diagnose it.
> 
> ...


Thanks! I definitely want to let the technicians take care of it for as long as it's under warranty. I do want to get vagcom at some point for my GTI though since I plan on doing a headlight retrofit and I'll need vagcom to change the settings for the DRLs. 

Small update: Dealership called and said they got a "weird code" that basically none of the oxygen sensors are being recognized. VW told them to reset some code in the system manually and drive it around and see if it comes back, so that's what they're doing.


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## le0n (Jun 12, 2013)

if you can't communicate with a component, you test the connection or overlay a working harness to said components.

ask for the specific "weird code", odbii or manufacturer specific.


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## ~clover (May 18, 2014)

le0n said:


> if you can't communicate with a component, you test the connection or overlay a working harness to said components.
> 
> ask for the specific "weird code", odbii or manufacturer specific.


They called today and my sister talked to them. They said they're going to drive it some more and try and see if the code comes back. They at least seem to be trying to figure out what's wrong instead of throwing parts at it like the other dealer. If I get a chance to talk to them again I'll find out what that code was. If not, I'm sure it'll be on the bill in the explanation area.


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## le0n (Jun 12, 2013)

cool, cool.

well at least you got a new alternator and o2 sensors from the last dealership. but it is annoying and inconvenient to have to go back and forth.


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## ~clover (May 18, 2014)

Well, apparently they couldn't get the light to come on again so they're giving the car back and said to bring it back when the light comes back on.


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## le0n (Jun 12, 2013)

~clover said:


> Small update: Dealership called and said they got a "weird code" that basically none of the oxygen sensors are being recognized. VW told them to reset some code in the system manually and drive it around and see if it comes back, so that's what they're doing.


Have her get this in writing; including the 'weird code'. If they got the code while diagnosing and cleared it and now are saying it's not coming up anymore. Ask them for proof that it is passing "readiness", i.e. what you'd need to pass any emissions test. It's when the ecm has had time to self-check all the potential errors to try to resolve them as temporary, intermittent or permanent faults.

Don't be surprised if the CEL comes back on when she drives it home.


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## ~clover (May 18, 2014)

le0n said:


> Have her get this in writing; including the 'weird code'. If they got the code while diagnosing and cleared it and now are saying it's not coming up anymore. Ask them for proof that it is passing "readiness", i.e. what you'd need to pass any emissions test. It's when the ecm has had time to self-check all the potential errors to try to resolve them as temporary, intermittent or permanent faults.
> 
> Don't be surprised if the CEL comes back on when she drives it home.


Thanks for the help. I couldn't get the specific code from them, but they did put everything in writing. They just said none of the sensors were recognized, VW tech support(huh?) told them to clear the code manually and see if it comes back. CEL hasn't come back on yet... I'm sure it will though.


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