The two accelerator-pedal position sensors disagree with each other. On the drive-by-wire 987 the DME uses redundant pedal sensors; when they lose correlation the DME defaults to reduced power / limp mode as a safety measure. Usually the pedal sensor assembly or its wiring.
SYMPTOMS
- Check-engine light
- Reduced power / limp mode
- Poor or dead throttle response
- Erratic idle
LIKELY CAUSES
- Faulty accelerator-pedal position sensor assembly
- Wiring/connector fault at the pedal
- Loss of reference voltage or ground
- Water/corrosion in the pedal connector
DIAGNOSIS STEPS
- Read both pedal-sensor voltages live - they should track proportionally
- Inspect the pedal connector and wiring for corrosion
- Check reference voltages and grounds
- Replace the pedal sensor assembly if signals don't correlate
RELATED PARTS
- Accelerator pedal position sensor
- Wiring harness