GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2008 🢒 SRX 🢒 Body Systems 🢒 Lighting 🢒 Park, License, and/or Tail Lamps Malfunction

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

Park Lamp Switch ON Signal

2

2

2

--

Park Lamp Relay Control

1

1

B2585 00

--

License Lamp Control

1

1

1

--

Park Lamp Control

1

1

1

--

License Lamp Ground

--

1

1

--

Park Lamps - LF Ground

--

1

1

--

Park Lamps - RF Ground

--

1

1

--

Tail/Stop and Turn Signal Lamps - LR Ground

--

1

1

--

Tail/Stop and Turn Signal Lamps - RR Ground

--

1

1

--

Turn Signal/Multifunction Switch Ground

--

2

2

--

1. Park, License, and/or Tail Lamps Malfunction

2. Park Lamp Switch Malfunction

Circuit/System Description

Battery positive voltage is applied at all times to both the coil and switched sides of the PARK LAMP relay. Ground is applied from G200 to the multifunction switch at all times. When the headlamp switch is placed in either the HEAD or PARK position, ground is applied to the park lamp relay control circuit. This energizes the PARK LAMP relay and applies battery positive voltage to all of the park, tail, license, and marker 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 for scan tool information

Circuit/System Verification

Ignition ON, observe the scan tool Park Lamp Switch parameter while cycling the park lamp switch between the ON and OFF positions. The readings should toggle between Active and Inactive.

⇒If the readings do not change between the commanded states, refer to Park Lamp Switch Malfunction.

Circuit/System Testing

Park Lamp Switch Malfunction

  1. Ignition OFF, disconnect the X1 harness connector at the turn signal/multifunction switch.
  2. Ignition OFF, verify that a test lamp illuminates between B+ and the ground circuit terminal K.
    3. ⇒If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify the scan tool Park Lamp Switch parameter is Inactive.
    4. ⇒If not the specified value, test the signal circuit terminal M for a short to ground. If the circuit tests normal, replace the BCM.
  4. Install a 3A fused jumper wire between the signal circuit terminal M and ground. Verify the scan tool Park Lamp Switch parameter is Active.
    5. ⇒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 BCM.
  5. If all circuits test normal, test or replace the turn signal/multifunction switch.

Park, License, and/or Tail Lamps Malfunction

  1. Ignition OFF, remove the fuse of the inoperative park, license, or marker lamps and inspect.
    2. ⇒If the fuse is OPEN, test the voltage supply circuit of the blown fuse for a short to ground.
  2. Ignition OFF, disconnect the park lamp relay.
  3. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 87 and ground.
    4. ⇒If the test lamp illuminates, test the control circuit for a short to voltage.
  4. Verify that a test lamp illuminates between the B+ circuit terminal 30 and ground.
    5. ⇒If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test the control circuit terminal 87 for a short to ground. If the circuit tests normal, test or replace the park lamp relay.
  5. Verify that a test lamp illuminates between the B+ circuit terminal 85 and ground.
    6. ⇒If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.
  6. Disconnect the harness connector at the inoperative park, license, or marker lamp.
  7. Ignition OFF, exterior lamps OFF, test for less than 5.0 ohms between the ground circuit and ground.
    8. ⇒If greater than the specified range, test the ground circuit for an open/high resistance.
  8. Connect the harness connector at the inoperative park, license, or marker lamp.
  9. Connect a 10A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. Verify the park, license, and marker lamps are activated.
    10. ⇒If the lamps do not activate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the inoperative park, license, or marker lamp.
  10. Connect a test lamp between the B+ circuit terminal 85 and the control circuit terminal 86.
  11. Command the Park Lamps ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
    12. ⇒If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the BCM.
    ⇒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 BCM.
  12. If all circuits test normal, test or replace the park lamp relay.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Headlamp Replacement
    •  Rear License Lamp Replacement
    •  Tail Lamp Replacement
    •  Relay Replacement
    •  Turn Signal Multifunction Switch Replacement
    •  Front Side Marker Lamp Bulb Replacement
    •  Control Module References for BCM replacement, setup, and programming