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/Sunload Sensor Signal | B2645 03 | B2645 07 | B2645 07 | --
Ambient Light/Sunload Sensor Ground | -- | B2645 07 | -- | --
Left/Right DRL Relay Control | 2 | 1 | 1 | --
Left/Right DRL Control | 1 | 1 | 2 | --
1. Daytime running lamps (DRL) inoperative 2. Daytime running lamps (DRL) always ON

#### DRL With High Intensity Discharge (HID) headlamps RPO TT2/TT6

The body control module (BCM) receives a signal from the ambient light/sunload sensor indicating a low or high ambient outside light level. Under daylight conditions the BCM supplies a battery voltage to the DRLs. If the headlamps are illuminated the DRLs will not illuminate.

#### DRL Without High Intensity Discharge (HID) headlamps RPO TT4

The body control module (BCM) receives a signal from the ambient light/sunload sensor indicating a low or high ambient outside light level. Under daylight conditions the BCM grounds the daytime running lamps relay control circuit energizing the daytime running lamp relay - left and daytime running lamp relay - right. The now closed relay supplies voltage to the day time running lamps. If the headlamps are illuminated the DRLs 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 the ambient light sensor to simulate daylight conditions. With ignition ON, engine running, and the gear selector in drive, the daytime running lamps should illuminate.

### Circuit/System Testing

#### DRL Malfunction - with HID Headlamps RPO TT2/TT6

1. Supply sufficient light to simulate daylight conditions to the B10 Ambient Light Sensor.
2. Ignition ON, headlamp switch in the AUTOMATIC LIGHT position.
3. Observe the park lamps. The park lamps should not be illuminated.

⇒ | If the park lamps are illuminated, replace the B10 Ambient Light Sensor.

4. Ignition OFF, disconnect the harness connector of the appropriate inoperative headlamp.
5. Connect a test lamp between the DRL control circuit terminal 4 and ground.
6. Command the Left or Right Dedicated Daytime Running Lamp Command 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 voltage. If the circuit tests normal, replace the K9 Body Control Module (BCM).

⇒ | If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K9 Body Control Module (BCM).

7. Verify that a test lamp illuminates between the DRL ground circuit terminal 1 and B+.

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

8. If all circuits test normal, test or replace the appropriate inoperative daytime running lamp.

#### DRL Malfunction - without HID headlamps RPO TT4

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

⇒ | If the headlamps are illuminated, replace the B10 Ambient Light Sensor.

4. Ignition OFF, disconnect the appropriate KR42L Daytime Running Lamp Relay - Left or KR42R Daytime Running Lamp Relay - Right.
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 appropriate inoperative Daytime Running Lamp 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 Left or Right Dedicated Daytime Running Lamp Command 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 K9 Body Control Module (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 K9 Body Control Module (BCM).

10. Connect a 10 A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87.
11. Disconnect the harness connector at one of the daytime running lamps.
12. Verify that a test lamp illuminates between the DRL control circuit terminal 9 and ground.

⇒ | 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 terminal 1 and 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 appropriate inoperative daytime running lamp or relay.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Headlamp Automatic Control Ambient Light Sensor Replacement

• | Headlamp Replacement

• | Headlamp Bulb Replacement

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