Reverse Input Circuit
What does P0812 mean?
The P0812 code means the vehicle's onboard diagnostic system has detected: Reverse Input Circuit. This is a moderate severity code.
Common Symptoms
- Check Engine Light illuminated
- Reverse lights may not work
- Backup camera does not activate
- TCM does not recognize when reverse is selected
Probable Causes (Ranked by Likelihood)
- Faulty reverse light switch or sensor Very High
- Damaged wiring in reverse input circuit High
- Corroded connector at transmission range sensor Moderate
- TCM input circuit failure Low
Step-by-Step Diagnostic Procedure
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Check if reverse lights illuminate when the vehicle is in reverse
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Test the reverse light switch on the transmission with a multimeter
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Inspect wiring and connectors between the reverse switch and TCM
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Use a scan tool to verify TCM detects reverse gear selection in live data
Frequently Asked Questions
Why does P0812 affect my backup camera?
The backup camera is triggered by the reverse input signal. If the TCM or body control module does not receive a valid reverse signal, the camera will not activate.
Is the reverse switch easy to replace?
On most vehicles, the reverse light switch is mounted on the transmission and can be replaced in under an hour. Some vehicles may require partial fluid drainage.
Can P0812 cause shifting problems?
P0812 typically affects reverse detection features like backup lights and camera. It usually does not affect the actual mechanical engagement of reverse gear.