Backup Lamps Malfunction Automatic Transmission
Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
Diagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Ignition -- Reverse Relay | 1, 3 | 1, 3 | -- | -- |
Reverse Relay Control | 2, 4 | 1 | 1 | -- |
Backup Lamp Supply Voltage | 1 | 1 | 2, 4 | -- |
Ground -- Backup Lamp | -- | 1 | -- | -- |
1. Backup lamps inoperative 2. Backup lamps always ON 3. Backup alarm inoperative 4. Backup alarm always ON | ||||
Circuit/System Description
Battery voltage is supplied to the REVERSE relay from the EGN-3 fuse located in the underhood fuse block. Ignition voltage is also supplied to the relay from the TRN/BCK/UP fuse (C4/C5) or Circuit Breaker 22 (C6/C7/C8) located in the I/P-1 fuse block. When the transmission is placed in the REVERSE position, the transmission control module (TCM) grounds the reverse relay control circuit which energizes the reverse relay. With the relay energized, the switch side contacts close and provide battery voltage to the backup lamps. The backup lamps are permanently grounded at G203. With both power and ground the backup lamps illuminate. Once the driver moves the gear selector out of the REVERSE position, the TCM removes ground from the reverse relay control circuit. This opens the reverse relay switch contacts turning OFF the backup lamps.
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
Exterior Lighting Systems Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
Engine running, shift the gear selector IN and OUT of reverse. The backup lamps should turn ON and OFF and the backup alarm should sound when changing between the specified states.
| ⇒ | If the backup lamps do not turn ON and OFF as specified, refer to Backup Lamps Circuit Test. |
| ⇒ | If the backup lamps operate as specified but the backup alarm does not sound, refer to Backup Alarm Circuit Test. |
Circuit/System Testing
Backup Lamps Circuit Test
- Ignition OFF, disconnect the REVERSE Relay.
- Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal F9 and ground.
- Verify that a test lamp illuminates between the ignition circuit terminal H9 and ground.
- Verify that a test lamp illuminates between the ignition circuit terminal H11 and ground.
- Disconnect the harness connector at the appropriate tail lamp assembly.
- Ignition OFF, test for less than 5.0 ohms of resistance between the ground circuit terminal E and ground.
- Connect the harness connector at the tail lamp assembly.
- Connect a 10A fused jumper wire between the ignition circuit terminal H11 and the control output circuit terminal F9. Verify the backup lamps are illuminated.
- Connect a test lamp between the control circuit terminal F11 and B+.
- Engine running, shift the gear selector IN and OUT of reverse. The test lamp should turn ON and OFF when shifting in and out of reverse.
- If all circuits test normal, test or replace the reverse relay.
| ⇒ | If the test lamp illuminates, test the control circuit for a short to voltage. |
| ⇒ | If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. |
| ⇒ | If the test lamp does not illuminate, test the ignition circuit for an open/high resistance. If the circuit tests normal and the ignition fuse is open, test the control circuit terminal F9 for a short to ground. If the circuit tests normal, test or replace the reverse relay. |
| ⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
| ⇒ | If the backup lamps do not illuminate, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, test or replace the backup lamp bulb or lamp assembly. |
| ⇒ | If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the TCM. |
| ⇒ | If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the TCM. |
Backup Alarm Circuit Test
- Ignition OFF, disconnect the harness connector at the backup alarm.
- Test for less than 1 ohm between the ground circuit terminal B and ground.
- Engine running with the gear selector in the REVERSE position, verify that a test lamp illuminates between the control circuit terminal A and ground.
- If all circuits test normal, test or replace the backup alarm.
| ⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
| ⇒ | If the test lamp does not illuminate, test the control circuit for an open/high resistance. |
Component Test
Relay
- Ignition OFF, disconnect the appropriate relay.
- Test for 70-100 ohms between terminals 85 and 86.
- Test for infinite resistance between the following terminals:
- Test for less than 5.0 ohms between terminals 30 and 87A.
- Install a 10A fused jumper wire between relay terminal 85 and 12 volts. Install a jumper wire between relay terminal 86 and ground. Test for less than 5.0 ohms between terminals 30 and 87.
| ⇒ | If the resistance is not within the specified range, replace the appropriate relay. |
| • | 30 and 86 |
| • | 30 and 87 |
| • | 30 and 85 |
| • | 85 and 87 |
| ⇒ | If not the specified value, replace the appropriate relay. |
| ⇒ | If greater than the specified range, replace the appropriate relay. |
| ⇒ | If greater than the specified range, replace the appropriate relay. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for TCM replacement, setup, and programming |
Backup Lamps Malfunction Manual Transmission
Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
Diagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Backup Lamp Switch B+ | 1 | 1 | -- | -- |
Backup Lamp Control | 1 | 1 | 1 | -- |
Backup Lamps Ground | -- | 1 | -- | -- |
1. Backup lamps Malfunction | ||||
Circuit/System Description
Battery voltage is applied to the backup lamp switch when the ignition switch is in the RUN or CRANK position. When the transmission is placed in REVERSE, the backup lamp switch contacts close providing battery voltage to the backup lamps. The backup lamps are permanently grounded at G203. With both power and ground the backup lamps illuminate. Once the driver moves the gear selector out of the REVERSE position, the backup lamp switch contacts open and the backup lamps turn OFF.
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
Exterior Lighting Systems Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the appropriate tail lamp assembly.
- Ignition OFF, test for less than 5 ohms between the ground circuit terminal E and ground.
- Connect the harness connector at the tail lamp assembly.
- Ignition OFF, disconnect the harness connector at backup lamp switch.
- Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal A and ground.
- Verify that a test lamp does not illuminate between the control circuit terminal B and ground.
- Connect a 10A fused jumper between the B+ circuit terminal A and the control circuit terminal B. Verify that the backup lamps are illuminate.
- If all circuits test normal, test or replace the backup lamp switch.
| ⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
| ⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. |
| ⇒ | If the test lamp illuminates, test the control circuit for a short to voltage. |
| ⇒ | If the backup lamps are not illuminated, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, test or replace the backup lamp. |
Component Testing
Backup Lamp Switch
- Ignition OFF, disconnect the harness connector at the backup lamps switch.
- Test for infinite resistance between terminal A and terminal B with the switch in the open position.
- Test for less than 2 ohms between terminal A and terminal B with the switch in the closed position.
| ⇒ | If less than the specified range, replace the backup lamp switch. |
| ⇒ | If greater than the specified range, replace the backup lamp switch. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
