D16/D20 - Manual Transmission
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
Typical Scan Tool Data
Circuit/System Description
The Backup Lamp (Reverse Position) switch is a two wire switch mounted on the transmission assembly. The Backup Lamp switch is connected to a 12 V signal circuit from the engine control module (ECM). The ground circuit is connected to chassis ground. The Backup Lamp switch is a normally open switch. The voltage on the Backup Lamp switch signal circuit to the ECM is HIGH when the switch is open and LOW when the switch is closed. When the transmission is placed in the reverse position, the ECM sends a serial data message to the Body Control Module (BCM). The message indicates that the gear selector is in the reverse position. The BCM applies battery voltage to the backup lamps. When the gear selector is moved out of the reverse position, a message is sent by the ECM via serial data requesting the BCM to remove battery voltage from the backup lamp control circuit.
Conditions for Running the DTC
P0812
* DTC P0812 is not set.
* The system voltage is more than 9 V.
* The ignition is in the RUN position.
Conditions for Setting the DTC
P0812
The Backup Lamp switch signal circuit is high with the transmission in reverse.
Action Taken When the DTC Sets
DTC P0812 is a Type B DTC.
Conditions for Clearing the DTC
DTC P0812 is a Type B DTC.
Reference Information
Schematic Reference
Manual Transmission Schematics D16/D20 - Manual Transmission
Connector End View Reference
Component Connector End Views Fuel Pump and Level Sensor Assembly
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
Engine Control Module Scan Tool Information (LUW) Scan Tool Testing and ProceduresEngine Control Module Scan Tool Information (LUV) for scan tool information
Circuit/System Verification
1. If any other DTCs are set, diagnose them first. Refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle.
2. Ignition ON, observe the scan tool Backup Lamp switch parameter. The parameter should change states when the transmission is shifted into and out of reverse gear.
• If the Backup Lamp switch parameter does not change states
Refer to Circuit/System Testing below.
• If the Backup Lamp switch parameter does change states
3. After performing the above steps, verify that the DTC does not reset by operating the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions you observe from the Freeze Frame/Failure Records data. If the vehicle passes the Circuit/System Verification procedure, then STOP. Do not perform the Circuit/System Testing or Component Testing as this may result in an unnecessary part replacement. Refer to Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections.
Circuit/System Testing
1. Ignition OFF, disconnect the harness connector of the B16 Backup Lamp switch.
2. Ignition OFF, test for less than 5 ohms between the ground circuit terminal B on the B16 Backup Lamp switch harness connector and chassis ground.
• If greater than the specified value
Test the ground circuit for an open/high resistance. Repair as necessary.
• If less than the specified value
3. Ignition ON, test for 11-13 V on the signal circuit terminal A at the B16 Backup Lamp switch harness connector and ground.
• If not within the specified range
Test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
• If within the specified range
4. Install a 3 A fused jumper wire between the signal circuit terminal A and the ground circuit terminal B on the B16 Backup Lamp switch harness connector. Verify that the scan tool B16 Backup Lamp switch parameter changed states.
• If the B16 Backup Lamp switch did not change states
Replace the ECM.
• If the B16 Backup Lamp switch did change states
5. If all circuits test normal, test or replace the B16 Backup Lamp switch.
Component Testing
Static Test
1. Ignition OFF, disconnect the electrical harness connector of the B16 Backup Lamp switch.
2. With the Backup Lamp switch closed, measure for less than 2 ohms between the signal circuit terminal A and the ground circuit terminal B on the B16 Backup Lamp switch.
• If the resistance is greater than the specified value
Replace the B16 Backup Lamp switch.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the repair.
* Control Module References Control Module References
* Engine Control Module Programming and Setup (LUW) Testing and Inspection