Under heavy acceleration in 1st or 2nd my '05 2.0l 'balt SS/SC will suddenly enter limp mode (ENG PWR REDUCED) with a CEL code P0068- Throttle position and engine load do not agree: the ECM detected that the TPS value and engine load do not agree with the expected TPS value and engine load.

It happens pretty much randomly - the car will run fine for weeks at a time then out of the blue this will happen.

If I turn the engine off for about 5 minutes, I can run the car with the CEL on fine as long as I'm easy on the accelerator. If I leave the car overnight, the CEL will disappear and I can usually drive it fine but it's a crapshoot when the same problem will happen again.

I've taken it into the shop a number of times and they're pretty much at a loss.

The car has a K&N CAI on it from the previous owner. I've already cleaned the MAF sensor.

Any ideas? I'm considering replacing the K&N with a stock intake but not sure if that will help.

 

I am having the same problem. Have you checked and or cleaned your BARO and SCIP sensors? The BARO is easy to mess up when doing a oil change and the SCIP can get messed up with oil from the K&N CAI.

 

Is the BARO sensor the same as the TMAP sensor on the right end of the intake manifold?

Is the procedure for cleaning these the same as for cleaning the MAF sensor?

 

The BARO and SCIP share the same harness at the neck of the supercharger. The BARO floats above the oil filter and the SCIP is the first sensor you see on the top of the supercharger. They are very clost to each other. The SCIP is held in with one bolt, pull it out and check the gasket to see if its damaged, cracked or dried out. The BARO is held in place with a bracket with 2 bolts, check to see if the nipple of the sensor is free and clear. They can be cleaned with sensor cleaner, like you would use to clean your MAF. To test them use a scan tool to compare the readings; the BARO and the SCIP should read almost the same when the engine is not running.

 

My cobalt has this same problem i cleaned the sensors and still goes into limp mode it accelerates on its own even after buying a new throttle body.....subd for a answer

 

BUMP - Exact same problem on the way home yesterday, anybody know where to start?

 

Did you clean the throttle body? I had this problem last year, and all I needed was to clean my throttle body.
If so, replace it.