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Park, License, and/or Tail Lamps Malfunction



Park, License, and/or Tail Lamps Malfunction

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.



Diagnostic Fault Information






Circuit/System Description

The vehicle park, license, and tail lamps are controlled by the body control module (BCM) based on an input from the headlamp switch. The headlamp switch has 4 positions: Off, Auto, Park, and Headlamps. The default headlamp switch position is Auto, in which the BCM uses the ambient light sensor to determine when exterior lamps are needed. The Off portion of the headlamp switch is a momentary switch which overrides the automatic lamps and will turn off the vehicle lamps. The Park position of the headlamp switch will only illuminate the vehicle parking lamps. The Headlamp position of the headlamp switch will illuminate both the parking lamps, as well has the headlamps. With the headlamp switch in the Park position, the park lamp switch on signal circuit is grounded, prompting the BCM to turn on the exterior lamps, regardless of other factors such as ambient light.


When a park lamp request is received, the BCM grounds the park lamp relay control circuit. This energizes the coil in the PARK LP PCB relay, causing the relay switch to close. Battery voltage is then applied through the LT PARK and RT PARK LAMP fuses and the park lamp supply voltage circuits illuminating the exterior lamps.


Reference Information
Schematic Reference

Exterior Lights Schematics (Exterior Lights Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Exterior Lighting Systems Description and Operation (Exterior Lighting Systems Description and Operation)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Programming and Relearning (Programming and Relearning) for scan tool information


Circuit/System Verification

1. Ignition ON, observe the scan tool Parklamp Switch parameter while cycling the headlamp switch between the Park and Off positions. The parameter should cycle between Active and Inactive.

• If the parameter does not cycle between the specified values, refer to Headlamp Switch Circuit Test.

2. Ignition ON, command the Parking Lamps ON and OFF with a scan tool. Verify the park, license, and tail lamps turn ON and OFF between commanded states.

• If any of the parking lamps are always OFF or remain always ON, refer to the appropriate Park, License, and/or Tail Lamps Circuit Test - All Countries Except Japan, Korea, Taiwan or Japan, Korea, Taiwan Only.
• If just the license lamps on an Japan, Korean, Taiwan vehicle are always OFF, refer to License Lamps Circuit Test - Japan, Korea, Taiwan Only.




Circuit/System Testing

Caution: The high intensity discharge system produces high voltage and current. To reduce the risk of severe shocks and burns:

* Never open the high intensity discharge system ballast or the arc tube assembly starter.
* Never probe between the high intensity discharge system ballast output connector and the arc tube assembly.




Headlamp Switch Circuit Test
1. Ignition OFF, disconnect the harness connector at the headlamp switch.
2. Ignition OFF, verify that a test lamp illuminates between the ground circuit terminal 8 and B+.

• If the test lamp does not illuminate, test the ground circuit for an open/high resistance.

3. Ignition ON, verify the scan tool Parklamp Switch parameter is Inactive.

• If not the specified value, test the signal circuit terminal 2 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 2 and ground. Verify the scan tool Parklamp Switch parameter is Active.

• If not the specified value, test the signal circuit for a short to voltage or and open/high resistance. If the circuit tests normal, replace the BCM.

5. If all circuits test normal, test or replace the headlamp switch.



Park, License, and/or Tail Lamps Circuit Test - All Countries Except Japan, Korea, Taiwan
1. Ignition OFF, disconnect the PRK LAMP relay from the rear fuse block.
2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 104 and ground.

• If the test lamp illuminates, test the control circuits for a short to voltage.

3. Verify that a test lamp illuminates between the B+ circuit terminal 102 and ground.

• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.

4. Verify that a test lamp illuminates between the B+ circuit terminal 100 and ground.

• If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.

5. Connect a test lamp between the B+ circuit terminal 102 and the control circuit terminal 101.
6. Command the parking lamps ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

• 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.

7. Disconnect the harness connector at the inoperative lamp.
8. Ignition OFF, test for less than 5.0 ohms between the appropriate ground circuit terminal listed below and ground:

* Front park and marker lamp terminal A
* Tail lamp terminal C
* License lamp terminal B
* Middle park lamp terminal B (V4U)
* Rear park lamp terminal B (V4U or B9Q)


• If greater than the specified range, test the ground circuit for an open/high resistance.

9. Connect a test lamp between the inoperative lamp control circuit terminal listed below and ground:

* Front park and marker lamp terminal B
* Tail lamp terminal F
* License lamp terminal A
* Middle park lamp terminal A (V4U)
* Rear park lamp terminal A (V4U or B9Q)

10. Connect a 3A fused jumper wire between the B+ circuit terminal 100 and the control circuit terminal 104. Verify the test lamp is illuminated.

• If the test lamp does not illuminate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the bulb or lamp assembly.

11. If all circuits test normal, test or replace the park lamp relay.



Park, and/or Tail Lamps Circuit Test - Japan, Korea, Taiwan Only
1. Ignition OFF, disconnect the appropriate PRK LAMP relay or the RT PRK LAMP relay from the rear fuse block.
2. Ignition ON, verify that a test lamp does not illuminate between the appropriate control circuit terminal listed below and ground:

* PRK LAMP relay terminal 104
* RT PRK LAMP relay terminal 94


• If the test lamp illuminates, test the control circuits for a short to voltage.

3. Verify that a test lamp illuminates between the appropriate B+ circuit terminal listed below and ground:

* PRK LAMP relay terminal 102
* RT PRK LAMP relay terminal 90


• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.

4. Verify that a test lamp illuminates between the appropriate B+ circuit terminal listed below and ground:

* PRK LAMP relay terminal 100
* RT PRK LAMP relay terminal 93


• If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.

5. Connect a test lamp between the appropriate B+ circuit terminal and the control circuit terminal listed below:

* PRK LAMP relay terminal 102 and terminal 101
* RT PRK LAMP relay terminal 93 and terminal 92

6. Command the parking lamps ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

• 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.

7. Disconnect the harness connector at the inoperative lamp.
8. Ignition OFF, test for less than 5.0 ohms between the appropriate ground circuit listed below and ground:

* Front park and marker lamp terminal A
* Tail lamp terminal H
* License lamp terminal B
* Middle park lamp terminal B (V4U)
* Rear park lamp terminal B (V4U or B9Q)
* Position lamp terminal A (T72)
* Position lamp terminal H (T84)


• If greater than the specified range, test the ground circuit for an open/high resistance.

9. Connect a test lamp between the inoperative lamp control circuit listed below and ground:

* Front park and marker lamp terminal B
* Tail lamp terminal F
* License lamp terminal A
* Middle park lamp terminal A (V4U)
* Rear park lamp terminal A (V4U or B9Q)
* Position lamp terminal G

10. Connect a 3A fused jumper wire between the appropriate relay B+ circuit terminal and the control circuit terminal listed below. Verify the test lamp is illuminated.

* PRK LAMP relay terminal 100 and terminal 104
* RT PRK LAMP relay terminal 90 and terminal 94


• If the test lamp does 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 bulb or the lamp assembly.

11. If all circuits test normal, test or replace the park lamp relay.



License Lamp Circuit Test - Japan, Korea, Taiwan Only
1. Ignition OFF, disconnect the EXP LIC LAMP relay from the rear fuse block.
2. Ignition OFF, test for less than 5 ohms between the ground circuit terminal 9 and ground.

• If greater than the specified range, test the ground circuit for an open/high resistance.

3. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 10 and ground.

• If the test lamp illuminates, test the control circuit for a short to voltage.

4. Park lamps ON, verify that a test lamp illuminates between the control circuit terminal 6 and ground.

• If the test lamp does not illuminate, test the control circuit for an open/high resistance.

5. Park lamps ON, verify that a test lamp illuminates between the control circuit terminal 8 and ground.

• If the test lamp does not illuminate, test the control circuit for an open/high resistance.

6. Ignition OFF, disconnect the harness connector at the inoperative license lamp.
7. Ignition OFF, test for less than 5.0 ohms between the ground circuit terminal B and ground.

• If greater than the specified range, test the ground circuit for an open/high resistance.

8. Connect a test lamp between the control circuit terminal A and ground.
9. Connect a 3A fused jumper wire between the relay control circuit terminal 10 and B+. The test lamp should illuminate.

• If the test lamp does 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 bulb or the lamp assembly.

10. If all circuits test normal, test or replace the EXP LIC LAMP relay.



Component Testing


Headlamp Switch
1. Ignition OFF, disconnect the harness connector at the headlamp switch.
2. Test for less than 2.0 ohms between the signal terminal 2 and the ground terminal 8 with the switch in the Park position.

• If not the specified value, replace the headlamp switch.

3. Test for less than 2.0 ohms between the signal terminal 2 and the ground terminal 8 with the switch in the Headlamp position.

• If not the specified value, replace the headlamp switch.




Relay Test
1. Ignition OFF, disconnect the relay.
2. Test for 70-100 ohms between terminals 85 and 86.

• If the resistance is not within the specified range, replace the relay.

3. Test for infinite resistance between the following terminals:

* 30 and 85
* 30 and 86
* 30 and 87
* 85 and 87


• If not the specified value, replace the relay.

4. Install a 10A fused jumper wire between relay terminal 85 and B+. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 ohms between terminals 30 and 87.

• If greater than the specified range, replace the relay.




Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Headlamp Switch Replacement (Service and Repair)
* High Intensity Discharge Headlamp Replacement (Service and Repair)
* Headlamp Bulb Replacement (Service and Repair)
* Front Side Marker Lamp Bulb Replacement (Service and Repair)
* Park/Turn Signal Lamp Bulb Replacement (Service and Repair)
* Rear License Lamp Replacement (Service and Repair)
* Tail Lamp Replacement (Service and Repair)
* Relay Replacement (Attached to Wire Harness) (Relay Replacement (Attached to Wire Harness))Relay Replacement (Within an Electrical Center) (Relay Replacement (Within an Electrical Center))
* Programming and Relearning (Programming and Relearning) for BCM replacement, setup and programming


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