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Makes 🢒 Isuzu 🢒 2008 🢒 Isuzu MD F-Series 🢒 Body Systems 🢒 Lighting 🢒 Backup Lamps Malfunction

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

Ignition Voltage -- Backup Lamp Switch

1

1

1

--

Backup Lamp Control

1

1

--

--

Ground -- Backup Lamps

--

1

--

--

1. Backup Lamps Malfunction

Circuit/System Description

Battery voltage is applied to the backup lamp switch when the ignition switch is in the ON or RUN positions. When the transmission is placed in the REVERSE position, ignition voltage from Circuit Breaker 9 is applied through the backup lamp switch and the backup lamp control circuit illuminating the backup lamps. Ground for the backup lamps is provided at G400. 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

Exterior Lights Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

Ignition ON, place the transmission in the REVERSE position. The left and right backup lamps should be illuminated and the backup alarm should sound.

⇒If the back lamps do not illuminate, refer to the Backup Lamps Test.
⇒If the backup lamps illuminate but the backup alarm does not sound, refer to the Backup Alarm Test.

Circuit/System Testing

Backup Lamp Test

  1. Ignition OFF, disconnect the harness connector at the appropriate tail lamp assembly.
  2. Ignition OFF, exterior lamps OFF, test for less than 5.0 ohms between the ground circuit terminal E and ground.
    3. ⇒If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Connect the harness connector at the tail lamp assembly and disconnect the harness connector at the backup lamp switch.
  4. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal A and ground.
    5. ⇒If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.
  5. Verify that a test lamp does not illuminate between the control circuit terminal B and ground.
    6. ⇒If the test lamp illuminates, test the control circuit for a short to voltage.
  6. Connect a 10A fused jumper wire between the ignition circuit terminal A and the control circuit terminal B. The backup lamps should illuminate.
    7. ⇒If the backup lamps do not illuminate, test the control circuit terminal B for a short to ground or an open/high resistance. If the circuit tests normal, test or replace the backup lamp bulb.
  7. If all circuits test normal, test or replace the backup lamp switch.

Backup Alarm Test

  1. Ignition OFF, disconnect the harness connector at the backup alarm.
  2. Test for less than 5.0 ohms between the ground circuit terminal B and ground.
    3. ⇒If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Connect a test lamp between the control circuit terminal A and ground.
  4. Ignition ON, place the transmission in the REVERSE position, the test lamp should illuminate.
    5. ⇒If the test lamp does not illuminate, test the control circuit for an open/high resistance.
  5. If all circuits test normal, test or replace the backup alarm.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Backup Lamp Switch Replacement
    •  Tail Lamp Bulb Replacement
    •  Tail Lamp Replacement

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

Backup Lamp Relay Control

1

1

1

--

Backup Lamp Voltage Supply

1

1

1

--

Backup Lamp Relay B+ Supply

1

1

--

--

Backup Lamp Ground

--

1

--

--

1. Backup Lamps Malfunction

Circuit/System Description

Ignition voltage from Circuit Breaker 9 is applied to the REVERSE Relay with the ignition in the ON or RUN positions. When the transmission is placed in the REVERSE position, the transmission control module (TCM) grounds the backup lamp relay control circuit which energizes the reverse relay. With the relay energized, the switch side contacts close and battery voltage is applied through the backup lamps control circuit illuminating the backup lamps. Ground for the backup lamps is provided at G400. Once the driver moves the gear selector out of the REVERSE position, the TCM removes ground from the backup lamp relay control circuit. This opens the backup lamps relay switch contacts turning OFF the backup lamps.

Reference Information

Schematic Reference

Exterior Lights Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Control Module References

Circuit/System Verification

Ignition ON, place the transmission in the REVERSE position. The left and right backup lamps should be illuminated and the backup alarm should sound.

⇒If the back lamps do not illuminate, refer to the Backup Lamps Test.
⇒If the backup lamps illuminate but the backup alarm does not sound, refer to the Backup Alarm Test.

Circuit/System Testing

Backup Lamps Test

  1. Ignition OFF, disconnect the reverse relay.
  2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 87 and ground.
    3. ⇒If the test lamp illuminates, test the control circuit for a short to voltage.
  3. Verify that a test lamp illuminates between the ignition circuit terminal 30 and ground.
    4. ⇒If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal and Circuit Breaker 9 is open, test the control circuit terminal 87 for a short to ground. If the circuit tests normal, test or replace the reverse relay.
  4. Verify that a test lamp illuminates between the ignition circuit terminal 85 and ground.
    5. ⇒If the test lamp does not illuminate, test the ignition circuit for an open/high resistance.
  5. Disconnect the harness connector at the appropriate tail lamp assembly.
  6. Ignition OFF, exterior lamps OFF, test for less than 5.0 ohms between the backup lamp ground circuit terminal E and ground.
    7. ⇒If greater than the specified range, test the ground circuit for an open/high resistance.
  7. Connect the harness connector at the tail lamp assembly.
  8. Ignition ON, connect a 10A fused jumper wire between the ignition circuit terminal 30 and the control circuit terminal 87. Verify the backup lamps are illuminated.
    9. ⇒If the backup lamps are not illuminated, test the control circuit terminal 87 for an open/high resistance. If the circuit tests normal, test or replace the backup lamp bulb.
  9. Connect a test lamp between the ignition circuit terminal 85 and the relay control circuit terminal 86.
  10. Shift the vehicle in and out of REVERSE. The test lamp should turn ON and OFF when shifting in and out of REVERSE.
    11. ⇒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.
  11. If all circuits test normal, test or replace the reverse relay.

Backup Alarm Test

  1. Ignition OFF, disconnect the harness connector at the backup alarm.
  2. Test for less than 5.0 ohms between the ground circuit terminal B and ground.
    3. ⇒If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Connect a test lamp between the control circuit terminal A and ground.
  4. Ignition ON, place the transmission in the REVERSE position, the test lamp should illuminate.
    5. ⇒If the test lamp does not illuminate, test the control circuit for an open/high resistance.
  5. If all circuits test normal, test or replace the backup alarm.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Relay Replacement
    •  Tail Lamp Bulb Replacement
    •  Tail Lamp Replacement
    •  Control Module References for TCM replacement, setup, and programming