P0812 moderate

Reverse Input Circuit

The P0812 code means the vehicle's onboard diagnostic system has detected: Reverse Input Circuit. This is a moderate severity code.

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Keep driving?: Short distances only
DIY difficulty: moderate
Estimated cost: $50 - $350 (parts and labor)

Check Your Fluid First

ANCEL AD310 OBD-II Scanner

Read and clear transmission codes. Many trans codes are caused by low or burnt fluid -- check level and color before assuming the worst.

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Read Transmission Codes

LAUNCH CRP123X (Reads All Systems)

Basic scanners only read engine codes. This reads transmission, ABS, and airbag too.

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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

Check if reverse lights illuminate when the vehicle is in reverse
Test the reverse light switch on the transmission with a multimeter
Inspect wiring and connectors between the reverse switch and TCM
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.