P0851moderate severityPowertrain
Park/Neutral Switch Input Circuit Low
on 2002 Audi A6 3.0L V6 · AWD
What this code means
The PCM sees a low voltage input from the park/neutral position switch. This may affect starting and gear-related engine functions.
Symptoms
- No-start in Park or Neutral
- Incorrect gear display
- Backup lights inoperative
Common causes
- Faulty park/neutral switch
- Short to ground in circuit
- Loose or corroded connector
- Failed transmission range sensor
Diagnostic steps
- Retrieve codes and check freeze frame
- Inspect PNP switch wiring for shorts
- Test switch continuity across gear positions
- Replace faulty switch or sensor
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