Backup Lamps Inoperative

BACKUP LAMPS INOPERATIVE

DIAGNOSTIC FAULT INFORMATION





Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure Initial Inspection and Diagnostic Overview.

CIRCUIT/SYSTEM DESCRIPTION
The Park/Neutral Position (PNP) switch controls the supply voltage for the back up lamps. When the gear shifter is in the reveres position the PNP switch is closed and power is supply to the backup lamps.

DIAGNOSTIC AIDS
- Check the backup lamps for proper operation
- An open/high resistance or short to ground in the backup lamps supply circuit would cause the concern.

CIRCUIT/SYSTEM VERIFICATION
Ignition ON engine OFF, turn the back up lamps ON and OFF by placing the gear shifter from Park to Reverse back to Park, while observing the back up lamps, the back up lamps should turn on when the gear shifter is in reverse.

CIRCUIT/SYSTEM TESTING
1. Ignition OFF, disconnect the harness connector at the PNP switch.
2. Ignition ON, verify that a test lamp illuminates between the voltage supply circuit and ground.
- If the test lamp does not illuminate, repair the voltage supply circuit for a short to ground or an open/high resistance. If the voltage supply circuit fuse is open, also test the signal circuit for a short to ground.
3. Verify that the backup lamps are OFF.
- If the backup lamps are not OFF, test the signal circuit for a short to voltage.
4. Install a 3-amp fused jumper wire between the signal circuit and the voltage supply circuit. Verify that the backup lamps are ON.
- If the backup lamps are not ON, test the signal circuit for an open/high resistance.
5. If all circuits test normal, test or replace the PNP switch.

COMPONENT TESTING
1. Ignition OFF, disconnect the harness connector at the PNP switch.
2. Test for infinite resistance between the signal terminal and the voltage supply terminal with the switch in the open position.
- If less than infinite resistance, replace the PNP switch.
3. Test for less than 2 ohms of resistance between the signal terminal and the voltage supply terminal with the switch in the closed position.
- If greater than 2.1 ohms, replace the PNP switch.

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