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Discussion Starter #1
06 Cobalt LT - 126,xxx.

On and off over the last two years of ownership, I've occasionally gotten P2128 and P2138 trouble codes, more often than not going over an extreme bump / pothole. car goes into limp mode and (usually) the code can be cleared and can get back on the road.

I recall seeing a couple of threads indicating that a possible cause is corrosion on ground points. I'm wondering if anyone has a list of possible ground points to check out (pictures would be great), and in particular how to get at the ground below the drivers seat? That's one I've seen mentioned but not yet tackled.

TIA.
 

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P2128 Accelerator Pedal Position (APP) Sensor 2 Circuit High Voltage ECM, PCM
P2138 Accelerator Pedal Position (APP) Sensor 1-2 Correlation ECM, PCM

If you think it's a ground then you would have to check the one near the steering column because those are accelerator pedal position error codes..
 

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Discussion Starter #3 (Edited)
If you think it's a ground then you would have to check the one near the steering column because those are accelerator pedal position error codes..
Probably a dumb question but where is the ground near the steering column?

Thus far I've replaced the APP sensor (twice), pulled can checked the BCM fuse and GM lan connections (believe those are the proper names) as pictured in this post, and cleaned this ground.

I thought a ground was the next thing to start checking if the last two things didn't solve the problem but any other suggestions of where to go next?
 

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Well I'm not sure you have either causes here if the problem only happens when you hit a big bump. I would look for a frayed wire in the harness going to the APP sensor. This wire is probably touching ground from the force of the impact.
 

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I'd say 70% of the time it's been over a bump, the rest of the time it just happens during normal driving or even a minute or two after start up. It's a tight squeeze down there but I don't see any frayed or exposed wires in the harness.
 

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The APP sensor wire go through the firewall all the way to the ECM so it could be a frayed wire in the engine bay too!
 
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