I have a 2004 Pontiac Grand Prix GTP with about 140k miles on it that goes into reduce engine power mode occasionally. I think it only does it going up hill, but not every hill. Repair shop said throttle body $900. I replaced it myself as well as the accelerator pedal sensor (due to the codes that pop up) and I am still receiving the same codes. (P1125 and P2138)
I have reset the codes with the reader. I haven’t checked the air filter myself, but my wife took it in for an oil change since this started happening. I would hope they’d check that. I’ll check tonight. I’ll get the reduced power and the codes now. “check stability” light has popped on when this occurs, but not every time.
Do you notice any engine pinging when going uphill? That can sound just like its name, a “ping” noise, often not very loud, that increases in frequency the faster the engine is going. Or if it gets worse, it can also sound louder, and like someone is rattling a metal soup can filled with nickles in the engine compartment. A quite noticeable clattering sound in other words.
I broke down and took it to a shop. They said I need to take it to the dealer and have them program the throttle body. Is there a way I can do this, or just have dealer do it? Also, does the accelerator pedal sensor need to be calibrated or reset?
Those fault codes relate to the accelerator pedal position sensor, nothing to do with the exhaust system. As mentioned before the wiring and connectors should be closely examined and tested, it may be worth the money to have an experienced technician repair this.
P0128 is related to the coolant temperature being too low, the thermostat may not be closing/sealing properly.