I have a 2004 Aveo, Automatic. I'm hoping someone can help me because I'm out of ideas. I was driving down the road recently (runs fine, 60k miles) and the Check Engine Light came on and it's throwing P0452 and P0122 (and P0700). It won't shift into 4th gear nor lock up. It shifts hard when putting it into Drive or Park or Reverse.
P0122 Is the Throttle Position Sensor, and the ECM is not supplying the 5v reference voltage. Instead the reference voltage is about 0.23v. Checked and replaced wiring, measured resistance, etc. The service manual says the ECM should be replaced. Tried that, still throwing same codes, still not supplying the correct 5v.
P0452 is the Evap System Pressure (Tank Pressure) low voltage. Same problem. Not supplying 5v reference.
Checking more of the service manual it says the Transmission Control Module (TCM) should be supplying 12v on one of the circuts to the ECM, but it's only supplying 2.6v instead of 12! So I replaced the TCM, and THAT didn't make a difference.
Why the heck are these computers not providing the correct reference voltage even when replaced?!
The TPS is simple : 5v, one ground, which goes through the TPS resistor and returns a value less than 5v. Yet my ECM, and replacement ECM isn't showing 5v. The scan tool even shows the pedal moving, just no where near as far as it's supposed to at 100%.
I'm totally stumped. This car is in great shape and only 60k miles and I'm ready to part it out because of these computer problems.
Lastly, when I clear the codes, the P0122 and P0452 will not clear. Both codes set again immediately after clearing. I don't even need to start the engine to set these codes.
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