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

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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 vehicle speed sensor faults exist.

* Reverse switch is ON.

Conditions for Setting the DTC

The ECM detects circuit malfunction of the reverse input switch.

Action Taken When the DTC Sets

DTC P0812 00 is Type C DTC.

Conditions for Clearing the DTC

DTC P0812 00 is Type C DTC.

Reference Information

Schematic Reference

Manual Transmission Schematics M20/M32 - Manual Transmission

Connector End View Reference

Component Connector End Views Sunshade - Left (DH6)

Description and Operation

Transmission System Description and Operation Transmission System Description and Operation

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

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References Control Module References 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 B16 Backup Lamp Switch.

2. Ignition OFF, test for less than 5 ohms between the ground circuit terminal 2 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 1 for a short to ground. If the circuit tests normal, replace the K20 Engine Control Module.

4. Ignition ON, install a 3 A fused jumper wire between the signal circuit terminal 1 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 K20 Engine Control Module.

5. If all circuits test normal, test or replace the B16 Backup Lamp Switch.

Repair Instructions

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

* Backup Lamp Switch Replacement M20/M32 - Manual Transmission

* Control Module References Control Module References for ECM replacement, programming and setup