P0812

DTC P0812

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.

DTC Descriptor
DTC P0812
- Reverse Position Switch Circuit

Diagnostic Fault Information





Circuit/System Description

The reverse gear switch is a normally open switch that closes with the reverse gear engagement. When the switch is open the engine control module (ECM) should detect a high signal voltage input. When the switch is closed the ECM should detect a low signal voltage input.

Conditions for Running the DTC

* No VSS faults exist.
* Reverse switch is ON.

Conditions for Setting the DTC

The ECM detects circuit failure of the reverse input switch.

Action Taken When the DTC Sets

DTC P0812 is type C DTC.

Conditions for Clearing the DTC

DTC P0812 is type C DTC.

Reference Information
Schematic Reference

Exterior Lights Schematics (with WHB) (Exterior Lights Schematics (with WHB))Exterior Lights Schematics (without WHB) (Exterior Lights Schematics (without WHB))
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Exterior Lighting Systems Description and Operation (Exterior Lighting Systems)
Electrical Information Reference

* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)

Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information

Circuit/System Verification

Ignition ON, observe the scan tool Reverse Switch parameter. The reading should be Off and change to On when the transmission is shifted into reverse.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the reverse switch.
2. Ignition OFF, test for less than 1 ohm between the ground circuit terminal 1 and ground.

• If greater than the specified value, test the ground circuit for an open/high resistance.

3. Ignition ON, verify the scan tool Reverse Switch parameter is Off.

• If not the specified value, test the signal circuit terminal 2 for a short to ground. If the circuit tests normal, replace the ECM.

4. Ignition ON, install a 3-amp fused jumper wire between the signal circuit terminal 2 and ground. Verify the scan tool Reverse Switch parameter is On.

• If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.

5. If all circuits test normal, test or replace the reverse switch.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

Control Module References (Programming and Relearning) for the ECM replacement, setup, and programming