For 1990-2009 cars

### Exterior Lamps

The exterior lighting system consists of the following lamps:

• | The headlamps

• | The daytime running lamps

• | The fog lamps

• | The park, tail and marker lamps

• | The turn signal lamps

• | The hazard lamps

• | The stop lamps

• | The backup lamps

### PCB Relays

This vehicle is equipped with the following printed circuit board PCB mounted relays.

• | High beam

• | Low beam

• | DRL

• | Fog lamp

• | Park lamp

• | Stop lamp

• | Horn relay

They are directly soldered to the underhood fuseblock circuit board. A failure of one of these relays will require the whole underhood fuseblock to be replaced.

### Headlamps

The headlamp switch is part of the turn signal multifunction switch.

The headlamps may be turned on 2 different ways. First, when the driver places the headlamp switch in the ON position, for manual operation. Second, with the headlamp switch placed in the AUTO position activating automatic lamp control (ALC).

The Left High Beam 10A fuse, Right High Beam 10A fuse, Left Low Beam 10A fuse, Right Low Beam 10A fuse, DRL 1 15A fuse, and DRL 2 15A fuse in the fuse block - underhood, supply battery positive voltage to both low and high beam lamps at all times. For manual operation, when the headlamp switch is in the ON position, the headlamp switch supplies ground directly to the headlamps and to the body control module (BCM) on the headlamp low or high beam signal circuit, depending on the position of the headlamp dimmer switch. The BCM uses this signal to determine if the conditions are present to illuminate the daytime running lamps or park lamps.

For ALC operation, the BCM receives a signal from the ambient light sensor indicating a low or high ambient, outside, light level. Under low light conditions the BCM grounds the headlamp relay control circuit energizing the headlamp control relay. The now closed relay supplies ground through the headlamp switch to the headlamps and the BCM on the headlamp low or high beam signal circuit, depending on the position of the headlamp dimmer switch. When the BCM grounds the headlamp relay control circuit it also grounds the park lamp relay control circuit illuminating the park lamps. The headlamp relay is grounded at G203.

If the engine stalls with the headlamps in the ALC mode under low light conditions, the headlamps will be controlled OFF during cranking.

The conditions necessary for the BCM to activate the ALC mode are as follows:

• | The ignition switch is in the RUN position.

• | The headlamps are in the AUTO position.

• | The park brake is released. If the park brake is applied after the ignition key is placed in the RUN position the ALC is not effected.

### Daytime Running Lamps (DRL)

The low beam headlamps operate at reduced intensity when in daytime running lamps (DRL) mode. The ground circuit to the switch side of 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 and to the BCM on the headlamp low beam signal circuit. The low beam headlamps now illuminate with reduced intensity. The DRL relay is grounded at G203. Any time the headlamps are illuminated the DRL will not illuminate. Manual park lamps do not effect DRL operation.

The conditions necessary for the BCM to illuminate the DRL are as follows:

• | The ignition switch is in the RUN position.

• | The headlamps are in the AUTO position.

• | The park brake is OFF, released.

• | The BCM is receiving a high light condition from the ambient light sensor.

• | The transmission is not in the PARK position.

### Fog Lamps

The FOG LP 10A fuse in the fuse block - underhood supplies battery positive voltage to the switch side of the fog lamp relay at all times. When the fog lamp switch is pressed, it supplies a momentary voltage signal on the front fog lamp switch signal circuit to the body control module (BCM). The BCM then supplies ground to the coil side of the fog lamp relay, energizing the relay. The switch side of the fog lamp relay then supplies voltage to both front fog lamps. The front fog lamps are connected to ground at G101. The park lamps or headlamps must be ON for the fog lamps to operate.

### Park, Tail and Marker Lamps

The park lamps consist of the park, tail, marker and license lamps. These lamps are illuminated any time the headlamp switch is in the PARK, ON position, or anytime the body control module (BCM) illuminates the headlamps. The PARK fuse in the fuse block - instrument panel (I/P) supplies voltage to both the coil and switch input side of the park lamp relay. The BCM controls the park lamp relay by grounding the park lamp control circuit energizing the relay.

For automatic lamp control (ALC) the BCM receives a signal from the ambient light sensor indicating a low or high ambient (outside) light level. Under low light conditions the BCM grounds the park lamp relay control circuit energizing the park lamp relay. The now closed relay supplies voltage on the park lamp supply voltage circuit directly to the lamps. The BCM always turns ON the park lamps and headlamps together when in the ALC mode.

For manual operation, when the headlamp switch is in the PARK position, the headlamp switch supplies ground to the BCM on the park lamp switch signal circuit. In response, the BCM grounds only the park lamp relay control circuit, and the lamps illuminate as stated above.

The conditions necessary for the BCM to activate the ACL mode are as follows:

• | The ignition switch is in the RUN position.

• | The headlamps are in the AUTO position.

• | The park brake is released. If the park brake is applied after the ignition key is placed in the RUN position the ALC is not effected.

### Turn Signal/Hazard Lamps

The body control module (BCM) is responsible for controlling the turn signals and hazard lamps. When the turn signal switch is placed in either the left turn or right turn position, the BCM receives a signal from the turn signal switch. The BCM then sends an on-off voltage signal to either the left or right turn signals and their instrument panel cluster (IPC) indicator. When the hazard switch is pressed, the BCM receives a signal from the hazard switch. The BCM then will send an on-off voltage signal to all the turn signal lamps. All the turn signal lamps will flash including both IPC turn signal indicators.

### Stop Lamps

The 15A Stop Lamp fuse located in the fuse block - underhood, supplies battery positive voltage to the normally open stop lamp switch. When the driver presses the brake pedal, the switch contacts close and battery positive voltage is supplied to both left and right stop lamp assemblies, the center high mounted stop lamp (CHMSL), the engine control module (ECM), and the throttle actuator control (TAC) module. The stop lamps are grounded at G401 and G403. The CHMSL is grounded at G301.

### Backup Lamps

The 15A CHMSL/BACKUP fuse in the fuse block - underhood supplies ignition positive voltage to the park/neutral position (PNP) switch of the automatic transmission. When the transmission is placed in reverse, the switch supplies voltage to the back up lamps and the inside rearview mirror. The back up lamps receive ground at G401 and G403.