From Ross-Tech Wiki
18047/P1639/005689 - Accelerator Position Sensor 1/2 (G79/G185): Implausible Signal
- Malfunction Indicator Light (MIL) ON
- Reduced Engine Output
- Wiring and/or connections faulty
- Faulty ECM
- Faulty Accelerator Pedal
- Check Measuring Block Readings for Accelerator Pedal
- Check Voltage Signals from ECM to Throttle Pedal (see factory repair manual)
- Check Wiring and Connectors from ECM to Accelerator Pedal
- There are 2 sensors in the accelerator pedal, both should increase in the same direction as the accelerator is pressed but they have different scales. This means one counts from 0 to 100, while the other one counts from 0 to 50.
- Accelerator Position Sensor faults can be caused by issues with the Oxygen Sensor(s) and it's wiring. Please verify this BEFORE replacing the ECM or Accelerator Pedal. Accelerator Pedal failure is very rare.