2006 Jetta TDI P0122, Flashing Glow Plug Light, Limp Mode

Hello and thanks for reading my post. I recently picked up a 2006 VW Jetta 1.9 TDI 5 speed manual. The EGR cooler was leaking so I deleted the EGR valve, ASV, and EGR cooler, then installed a race pipe. I have yet to tune it since I wanted to see how it did on fuel as a baseline (37 mpg for those interested). I've put 750 miles on it and the check engine light was of course on for the EGR.



All of a sudden, the accelerator pedal stopped responding yesterday while driving on the highway and the glow plug light started flashing, which I have found means there is an engine management fault. After getting ready to pull over and call a tow truck, it started working again, but the car was in limp mode.


I pulled the codes with by OBD2 scanner and got:


P0122: TPS/Pedal Position Sensor A Circuit Low Input
P0642: Sensor A Reference Voltage Circuit Low
P0101: MAF or VAF A CKT Range/Perf
P2413: EGR System Performance


Freeze Frame Data:



DTC that caused freeze frame: P2413
Throttle Position: 94.5%
Engine RPM: 0 RPM
Load Value: 0.0%
Air Flow Rate: 0.00 GR/sec
MAP sensor: 99 KPA
Coolant Temp: 77 F
Intake Air Temp: 71 F
Vehicle Speed: 0 MPH


I know a VAG-COM is the best way to get readings, but this is all I have at the moment. From my research, I've seen people say that this can be caused by a faulty accelerator pedal sensor, ASV, or even the ECU. Many threads that are started do not mention if the issue was solved and how. Any information on diagnosing this issue would be much appreciated. I saw mention of testing the pins on the pedal sensor, but no information on which pins and values. Thank you in advance for any and all advice.

It looks like you have a problem with the 5 volt reference, which could be caused by a shorted wire, or sensor or shorted ecm. I don't have access to the pin outs right now, since I'm not at the shop, but I'd recommend making sure your asv or EGR harnesses aren't rubbing on something and shorting out.
I'd recommend getting it tuned though as well, since having them merely disconnected will cause a malfunction indicator light to stay on.
But, your code for the accelerator pedal is also "low input" which means that the 5 volts it's supposed to get aren't there.

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Thank you for the quick reply. I'll check out the harnesses and make sure they are not grounding/shorting out on anything since I think I just tucked them behind the engine. Hopefully someone will be able to chime in with the pin outs so I can do a little testing. Thanks again

I just chased this in one of my 06 Jettas. I have 2 of these cars so the first thing I did was swap the pedal from the other car and nothing changed. The problem seemed to be that the connector at the pedal wasn't staying in contact with the pedal. I slightly bent the pins in the pedal to the side to sort of "force" them to scrape the connector when it was plugged in and it's been working ever since.

It can also (occasionally) be moisture or other contamination at the ECU plug/socket side of the wiring run...happened to me once.

But yup, in general the issues are down at the throttle end, where there is always lots of moisture/road salt/etc.

Thanks for the info. I checked the EGR and ASV valve harnesses and one of them was a bit charred from rubbing the exhaust, so it’s possible the pins in the connector were making contact. After checking that, I started the car and the flashing glow plug light was gone and it had full power. I cleared the codes, but the TPS code P0122 immediately came back, so I think there’s still something going on. I’m going to try and check the connector at my friend’s shop today and I will follow up with results.

Update:
I was able to remove the pedal today and test voltage at the connector. Based on another forum post, everything seems normal.

Pin 1 to ground: 4.99 V
Pin 2 to ground: 4.99 V
Pin 1 to 5: 4.99 V
Pin 2 to 3: 4.99 V

I decided to take the pedal apart and see if there was anything obvious. Try this at your own risk. There was a plastic rivet which had to be drilled out and I broke a few clips taking it apart, but it all went back together okay. I found that the circuit board was a bit loose in its housing. The only thing holding it in is the inside portion of the pins which are like spring steel “fingers” that contact the board. I removed the board and bent them down a bit so there would be a little more pressure, therefore better contact. I put it all back together and the code returned after clearing it, but the issue is not present at the moment. I will update if anything changes, which I suspect it may.

Additional info:
For anybody wondering how to remove the pedal from the floor, remove the plastic cover held on by 2 plastic screws. Then, take out the one torx bolt (T30, I think). Here’s the tricky part. There are two clips which need to be released with a thin screwdriver. The right side one, just push the screwdriver straight in and pull the pedal up. The left side one has a tab which needs to be moved to the right before pulling up.

Here’s a couple pics which may help someone in the future. I put a red arrow pointing at the “fingers” I bent down for better contact. And the picture of the pedal clips was taken from pelicanparts.com.







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Hesitation around 1800 RPM now

Update:

So the pedal has generally seemed to work since cleaning things up, however there is another issue which may or may not be related. When taking off slow in first gear, especially from a cold start, there is a hesitation/stumble around 1800 RPM. It starts to build boost, then stops, kind of jumps around a bit, and then takes off all of a sudden. I experienced this just once before the whole pedal ordeal. It seems that if I take off aggressively this does not happen. This situation go even worse as I was just driving home from work. I took off in first from a red light and is started to stumble as I was shifting into 2nd gear. Then in 2nd gear, it was all hesitation and would barely rev and move forward. I pushed the clutch in and revved it up and then dumped it and it took off and drove fine.


When I got home, I pulled the codes and all of the same codes are present, but P0101: MAF or VAF A CKT Range/Perf now appears first in the list, which usually means it's the major cause of the check engine light from my experience.



Does anybody have any experience with this hesitation? Is it linked to the accelerator pedal or is it more likely just coincidence that it's happening now? Any help is appreciated.

06JettaBRM said:

Update:

So the pedal has generally seemed to work since cleaning things up, however there is another issue which may or may not be related. When taking off slow in first gear, especially from a cold start, there is a hesitation/stumble around 1800 RPM. It starts to build boost, then stops, kind of jumps around a bit, and then takes off all of a sudden. I experienced this just once before the whole pedal ordeal. It seems that if I take off aggressively this does not happen. This situation go even worse as I was just driving home from work. I took off in first from a red light and is started to stumble as I was shifting into 2nd gear. Then in 2nd gear, it was all hesitation and would barely rev and move forward. I pushed the clutch in and revved it up and then dumped it and it took off and drove fine.


When I got home, I pulled the codes and all of the same codes are present, but P0101: MAF or VAF A CKT Range/Perf now appears first in the list, which usually means it's the major cause of the check engine light from my experience.



Does anybody have any experience with this hesitation? Is it linked to the accelerator pedal or is it more likely just coincidence that it's happening now? Any help is appreciated.

Click to expand...

Search the zip tie mod. That's pretty common for the brm motor.

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