05 Cobalt LT Need Help!

[Escort42]

I am a technician at a body shop (the only tech). Have a 2005 Cobalt with a 2.2L. Car has an intermittent check engine light. Only comes on on long drives. When it does, the car goes into limp mode and won't go over 35 mph. I've replaced the throttle body. Codes were the same before and after I replaced it. Here are the codes:
P0641-5 Volt Reference 1 Circuit.
P2135-Throttle Position Sensor 1-2 Correlation
P2138-Accelerator Pedal Position Sensor 1-2 Correlation.
These codes are under the MIL codes. But when I check current codes all I find is:
U2108-Lost Communication with ABS/TCS Control system BCM
(read that on another post so I hope that's what the code really means. Scanner says Description Unavailable.)
And when I was looking in Freeze Frame I found a code but it wasn't a stored DTC so my manager told me not to worry about it.
P0532-A/C Refrigerant Pressure Sensor Circuit.

Any help in where I should start looking/testing would be greatly appreciated. My shop doesn't have any computer diagnostics so everything pretty much comes out of my head or what I can find online. Thanks a bunch.

 

[zora]

Typically you go after the lower numerical codes because the higher ones may be secondary. The P0641 is pointing to an ECM issue. The other link refers to the same code but shows that a sensor shorting out to ECM can cause the issue. Doesnt your shop have access to professional resources with code diagnostic charts?

http://engine-codes.com/p0641_chevrolet.html

http://www.duramaxforum.com/forum/0...roblem-diagnosed-bad-ecm-gm-service-shop.html

 

[Escort42]

Trust me, I wish they did. Still messing with it. But without knowing which wires are what and which pins are in the ecm, it's kind of a hair pull out situation.