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
--- | --- | --- | --- | ---
DRL Indicator | 1 | 1 | -- | --
DRL Relay | B2602 | B2602 | B2603 | --
1. DRL Indicator Inoperative

### Circuit/System Description

The low beam headlamps operate at reduced intensity when in daytime running lamps (DRL) mode. The DRL relay is soldered into the underhood fuse block circuit board. The ground circuit to the switch side or the DRL relay has a resistor in-line to reduce the intensity of the low beam headlamps for DRL operation. 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 control relay. The now closed relay supplies ground directly to the low beam headlamps now illuminate with reduced intensity. The DRL relay is ground at G203. Any time the headlamps are illuminated the DRL will not illuminate. Manual park lamps do not effect DRL operation.

### Diagnostic Aids

An open/high resistance in the instrument panel I/P can cause the DRL indicator to become inoperative

### Reference Information

#### Schematic Reference

Headlights/Daytime Running Lights (DRL) Schematics

#### Connector End Views

Lighting Systems Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

• | Scan Tool Data Definitions

• | Scan Tool Data List

• | Scan Tool Output Controls

### Circuit/System Verification

Ignition ON, the headlamp switch in the AUTO position. Observe the headlamps, the headlamps should be ON.

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the turn signal multifunction switch terminals C1 pins 4 and 2.
2. Ignition ON, test for less than 1 ohm of resistance between the low reference circuit and ground with the DRL ON.

⇒ | If greater than 1 ohm, test the low reference circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the turn signal multifunction switch.

3. Test for battery voltage between the supply voltage circuit and ground.

⇒ | If battery voltage is not found, test the supply voltage circuit for a short to ground or an open/high resistance.

4. If all circuits test normal, replace the I/P.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for I/P replacement, setup, and programming