For 1990-2009 cars

### 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
--- | --- | --- | --- | ---
Ambient Light Sensor Signal | B2645 03 | B2645 07 | B2645 07 | --
Ambient Light Sensor Ground | -- | B2645 07 | -- | --
DRL Relay Control | 2 | 1 | B2600 00 | --
DRL 2 Relay Control | 2 | 1 | B2605 00 | --
Left DRL Control | 1 | 1 | 2 | --
Right DRL Control | 1 | 1 | 2 | --
1. Daytime Running Lamps (DRL) Inoperative 2. Daytime Running Lamps (DRL) Always ON

### Conditions for Running the DTC

The body control module (BCM) receives a signal from the ambient light sensor indicating a low or high ambient outside light level. Under daylight conditions the BCM grounds the DRL relay control circuit energizing the DRL relay. The now closed relay supplies voltage to the DRLs. Any time the headlamps are illuminated the DRL will not illuminate.

### Reference Information

#### Schematic Reference

Headlights/Daytime Running Lights (DRL) 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

Supply sufficient light to simulate daylight conditions to the ambient light sensor. Ignition ON, engine running, and the gear selector in drive. The DRLs should illuminate.

### Circuit/System Testing

#### DRL Malfunction - with RPO TSH/TVC/TVD

1. Supply sufficient light to simulate daylight conditions to the ambient light sensor.
2. Ignition ON, headlamp switch in the AUTO position.
3. Observe the headlamps. The headlamps should not be illuminated.

⇒ | If the headlamps are illuminated, replace the ambient light sensor.

4. Ignition OFF, disconnect the appropriate DRL relay.
5. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 87 and ground.

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

6. Verify that a test lamp illuminates between the B+ circuit terminal 86 and ground.

⇒ | 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 for a short to ground. If the circuit tests normal, test or replace the DRL relay.

7. Verify that a test lamp illuminates between the B+ circuit terminal 30 and ground.

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

8. Connect a test lamp between the B+ circuit terminal 86 and the control circuit terminal 85.
9. Command the DRL 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.

10. Connect a 10A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87.
11. Disconnect the harness connector at one of the DRLs.
12. Verify that a test lamp illuminates between the DRL control circuit listed below and ground:

• | RPO W49/Z88 terminal 1

• | RPO WDA terminal 2

⇒ | If the test lamp does not illuminate, test the control circuit for a short to ground or an open/high resistance.

13. Verify that a test lamp illuminates between the DRL ground circuit listed below and B+:

• | RPO WDA terminal 1

• | RPO W49/Z88 terminal 3

⇒ | If the test lamp does not illuminate, test the ground circuit for a open/high resistance.

14. If all circuits test normal, test or replace the DRL relay.

#### DRL Malfunction - without RPO TSH/TVC/TVD

1. Supply sufficient light to simulate daylight conditions to the ambient light sensor.
2. Ignition ON, headlamp switch in the AUTO position.
3. Observe the park lamps. The park lamps should not be illuminated.

⇒ | If the park lamps are illuminated, replace the ambient light sensor.

4. Ignition OFF, disconnect the DRL relay.
5. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 87 and ground.

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

6. Verify that a test lamp illuminates between the B+ circuit terminal 86 and ground.

⇒ | 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 for a short to ground. If the circuit tests normal, test or replace the DRL relay.

7. Verify that a test lamp illuminates between the B+ circuit terminal 30 and ground.

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

8. Connect a test lamp between the B+ circuit terminal 86 and the control circuit terminal 85.
9. Command the DRL 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.

10. Connect a 10A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87.
11. Disconnect the harness connector at one of the low beam headlamps.
12. Verify that a test lamp illuminates between the DRL control circuit listed below and ground:

• | RPO WDA terminal B

• | RPO Z88 terminal A

⇒ | If the test lamp does not illuminate, test the control circuit for a short to ground or an open/high resistance.

13. Verify that a test lamp illuminates between the DRL ground circuit listed below and B+:

• | RPO WDA terminal A

• | RPO Z88 terminal B

⇒ | If the test lamp does not illuminate, test the ground circuit for a open/high resistance.

14. If all circuits test normal, test or replace the DRL relay.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Daytime Running Lamp (DRL) Ambient Light Sensor Replacement

• | Control Module References for BCM replacement, setup, and programming