OBD-II Generic Error Code P0812: How to Fix It

Medium 1-2 hours Medium Severity Verified June 2026
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Error Code
P0812
Brand
OBD-II Generic
Product Type
automotive
Severity
Medium
DIY Difficulty
Medium
Estimated Fix Time
1-2 hours
Error code P0812 indicates that your vehicle's powertrain control module (PCM) has detected a problem with the reverse input circuit. This typically means the PCM is not receiving a signal when the transmission is shifted into reverse, which can affect backup lights and transmission operation.
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Tools You'll Need

How to Fix Error Code P0812

  1. Check Reverse Lights

    Ensure the vehicle is in park with the parking brake engaged before checking lights.

  2. Inspect Reverse Light Fuse

    Always disconnect the battery before handling fuses to avoid short circuits.

  3. Test Reverse Light Switch

    Ensure the engine is off and the transmission is in park before working near it.

  4. Inspect Wiring and Connectors

  5. Check Transmission Range Sensor

    Working on the transmission may require specialized tools; consult a professional if unsure.

  6. Scan for Additional Codes

Parts You May Need

Reverse Light Switch
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Transmission Range Sensor
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Reverse Light Switch
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Transmission Range Sensor
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Reverse Light Switch
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Transmission Range Sensor
Check Price on Amazon
Reverse Light Switch
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Transmission Range Sensor
Check Price on Amazon
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When to Call a Professional

If you have inspected the fuse, switch, and wiring but the code persists, or if you are uncomfortable working around the transmission, consult a professional mechanic. Additionally, if the transmission range sensor requires adjustment or internal transmission issues are suspected, seek expert help.

Frequently Asked Questions

What does error code P0812 mean?
P0812 indicates a malfunction in the reverse input circuit, meaning the PCM is not detecting when the transmission is in reverse.
Can I drive with a P0812 code?
It is generally safe to drive, but reverse lights may not work, and transmission shifting could be affected. Fix it promptly.
How do I test the reverse light switch?
Use a multimeter to check for continuity between the switch terminals when the transmission is in reverse. No continuity means the switch is faulty.
Where is the reverse light switch located?
It is usually mounted on the transmission, near the shift linkage or on the side of the gearbox.
Is P0812 a serious code?
It is moderately serious. It can lead to inoperative reverse lights and may affect transmission control, but it rarely leaves you stranded.

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