P0851
PowertrainTransmissionmoderate severityPark/Neutral Switch Input Circuit Low
What P0851 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
🔌 Don't have a code reader?
Any of these will read and clear this code — pick by how deep you want to go.
Budget handheld~$40
ANCEL AD410 →
No-phone-needed handheld — reads, clears, live data, freeze frame.
✓ ANCEL official store
Serious DIY~$100
BlueDriver Pro →
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SHOP FAVORITEShop-grade tablet~$300
Autel MaxiCOM MK808S →
Bidirectional tests, service resets, all systems.
✓ Autel official store
Pro diagnostics$1,500+
Autel MaxiSys MS906 Pro →
Full-system pro platform — topology mapping, ECU coding, the works.
✓ Autel official store
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