P0812 Fault Code

Reverse Input Circuit

• What does that mean?
• Symptoms
• Causes
• Solutions

The P0812 fault code indicates an issue with the reverse input circuit in a vehicle's transmission system. This code is typically logged when the Engine Control Module (ECM) detects a malfunction related to the reverse gear position sensor or its wiring. Proper functioning of the reverse input circuit is crucial for the correct operation of the vehicle's transmission, allowing it to shift into reverse smoothly.

• The reverse input circuit is responsible for signaling the transmission control module when the vehicle is in reverse.
• Malfunctions in this circuit can lead to erratic transmission behavior, impacting the vehicle's drivability.

What are the symptoms of the P0812 code?

Drivers may notice several symptoms when a P0812 fault code is logged:

• Difficulty in shifting into reverse or no response when attempting to engage reverse gear.
• Unusual noises or grinding when the transmission tries to shift into reverse.
• Warning lights illuminated on the dashboard, particularly the check engine light.
• General erratic behavior of the transmission, with possible slipping or harsh shifting when changing gears.

What causes the P0812 code?

Several potential causes may lead to a P0812 code being triggered:

• Damaged or frayed wiring or connectors in the reverse input circuit.
• A faulty reverse gear position sensor that fails to send accurate signals.
• Poor grounding or short circuits in the electrical system.
• Issues with the transmission control module itself that affect its ability to process signals from the input circuit.

How to fix P0812?

To resolve a P0812 fault code, the following steps should be taken:

• Conduct a thorough visual inspection of the reverse input circuit wiring and connectors for any signs of damage or corrosion.
• Test the reverse gear position sensor for proper operation; if faulty, it should be replaced.
• Check the transmission control module for any software updates or malfunctions that may need addressing.
• Clear the fault code and test drive the vehicle to ensure the issue has been resolved and the code does not reappear.