Exterior Lighting Systems Description and Operation. Chevrolet PJJ 2001

For 1990-2009 cars

### Exterior Lamps

The exterior lighting system consist of the following lamps:

• | The Headlamps

• | The Fog Lamps

• | The Park, Tail and Marker Lamps

• | The Turn Signal Lamps

• | The Stoplamps

• | The Backup Lamps

### Headlamps

The headlamps are operated when the driver places the headlamp switch in the ON position. The headlamp fuse supplies battery positive voltage from the fuse block to the left and right headlamps. The circuit continues through both low and high beam lamps, then to ground. The high beam circuits are connected together and provide the body control module (BCM) with a high beam input. The low beam and high beam circuits continue to the headlamp switch. The headlamp switch includes the dimmer switch and the flash-to-pass switch. When the headlamp switch is placed in the headlight ON position a path to ground is provided. Depending on the position of the high/low beam switch, either the low or high beam circuit will now have power and ground.

If the driver places the headlight switch in the ON position after the ignition switch has been turned OFF, or if the ignition switch is in the ACCY position, the headlights will remain on until turned off or the battery runs dead.

### Fog Lamps

With the ignition switch in the [ON] position, and the park lamps or low beam headlights on, the fog lights will illuminate when the driver presses [moves] the fog lamp switch. The fuse block supplies battery positive voltage to the fog lamp relay switch circuit. The fog lamp switch supplies battery positive voltage to the fog lamp relay coil. When the fog lamp switch is pressed, the fog lamp relay is then energize. The current flow is now from the fog lamp relay to both front fog lamps and to ground. The state of the fog lamps (either ON or OFF) will remain the same until the fog lamp switch is pressed [or moved] again, or the ignition switch is cycled OFF and ON. Fog lamp operation will be cancelled whenever the park lamps, are turned OFF.

### Park, Tail and Marker Lamps

The park, tail and marker lamps, including the license lamps, are turned on when the headlamp switch is placed in the PARK or HEADLAMP position, or anytime the headlights are requested. The fuse in the fuse block supplies battery positive voltage to the park lamp switch contacts. When the park lamps are turned on current flow is from the park lamp switch to their respective park and marker lamps. If the park lights are turned on after the ignition switch has been turned OFF, or is in the ACCY position, they will remain on until turned off or the battery runs dead.

### Remote Keyless Entry Exterior Lamp Illumination

When the remote function actuation (RFA) module receives a door unlock command from the remote function actuator transmitter, the RFA module will ground the door unlock signal circuit to the BCM, [send a class 2 message to the body control module (BCM),] indicating that an UNLOCK command has been received. The BCM will then flash the park lamps twice. With all the doors closed, and the RKE transmitter is used to lock the doors, the park lamps will flash twice. The park lamps will not flash if the rear compartment is opened using the RKE transmitter.

### Turn Signal Lamps

The fuse in the IP junction block supplies battery positive voltage to the flasher module, which is part of the hazard switch assembly. The turn signal lamps may only be activated with the ignition switch in the ON or ACCY position. When the turn signal switch is placed in either the left or right position, current flow is from the flasher module's output to the turn signal switch assembly. The flasher module 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, all the turn signal lamps will flash including both IPC turn signal indicators.

### Stop Lamps

The fuse in the junction block 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 and to the center high mounted stop lamp (CHMSL).

### Backup Lamps

The fuse in the junction block supplies battery positive voltage to the park/neutral position switch. When the driver places the gear selector lever in the REVERSE position, the current flow is from the park/neutral position switch to the backup lamps.