For 1990-2009 cars

### Exterior Lamps

The exterior lighting consist of the following lamps:

• | Headlamps

• | Fog lamps

• | Park, tail, license and marker lamps

• | Turn signal lamps

• | Hazard warning lamps

• | Stop lamps

• | Backup lamps

### Headlamps

The headlamps consist of 2 interchangeable single filament bulbs on each side of the vehicle which provide high and low beams. The lower bulb in the headlamp is the high beam and the upper bulb is the low beam.

The headlamps may be turned ON in two different ways:

• | When the headlamp switch is placed in the ON position, for normal operation

• | When the headlamp switch is placed in the AUTO position, for automatic lamp control (ALC)

The headlamp switch is supplied with voltage from the instrument panel cluster (IPC) by two signal circuits, the headlamps signal circuit and the park lamp signal circuit. When the headlamp switch is placed in either the AUTO or HEAD position, the headlamps signal circuit is provided with ground through the switch contacts of the headlamp switch to a common headlamp switch ground back to the IPC. The IPC interprets the flow of voltage and responds by sending a serial data message to the underhood electrical center (UEC) requesting either the low beam or high beam headlamps be activated. The UEC responds by applying voltage to the left and right low beam headlamp control circuits illuminating the low beam headlamps. Ground for the left headlamp is supplied at G101 and the right headlamp receives ground at G102. The position of the turn signal/multifunction switch which is integrated into the steering column module, determines which headlamps, high or low beam are activated by the UEC. The turn signal/multifunction switch contains functions that control the headlamp dimming functions, left and right turn signals, and flash to pass. To activate the high beam headlamps, the turn signal/multifunction switch is pushed forward. The steering column module interprets the position of the switch and sends a serial data message to the UEC requesting the high beams be activated. The steering column module also sends a serial data message to the IPC requesting the high beam indicator be illuminated.

### Automatic Lamp Control/Twilight Sentinel

To activate the automatic lamp control (ALC), the headlamp switch is placed in the AUTO position. During ALC the headlamps will be off during daylight conditions but will turn on when the ambient light sensor detects low outside light level. The ambient light sensor is a light sensitive transistor that varies the voltage signal to the underhood electrical center (UEC). When outside lighting conditions are low, The UEC applies voltage to the headlamp low beam control circuits and sends a serial data message to the rear electrical center (REC) requesting the rear park lamps be activated. The REC responds by applying voltage to the rear park lamp control circuits illuminating the rear park lamps.

### Flash to Pass (FTP)

The turn signal/multifunction switch is integrated into the steering column module. When the low beam headlamps are ON and the turn signal/multifunction switch is momentarily placed in the flash to pass (FTP) position, the steering column module responds by sending a serial data message to the underhood electrical center (UEC) requesting the high beams be activated. The UEC applies voltage to the high beam control circuit causing each high beam solenoid to retract a plate partially covering the low beam headlamps and allowing the lamps to illuminate at full brightness momentarily.

### Fog Lamps

The front fog lamp switch is supplied with voltage from the instrument panel cluster (IPC) via the front fog lamp switch signal circuit. The front fog lamp switch signal circuit is grounded momentarily by pressing the front fog lamp switch. The front fog lamp switch signal circuit is grounded through the switch contacts of the front fog lamp switch to a common headlamp switch ground back to the IPC. The IPC interprets the flow of voltage and responds by sending a serial data message to the underhood electrical center (UEC). The UEC responds by applying ground to the front fog lamp relay control circuit energizing the front fog lamp relay coil. With the front fog lamp relay coil energized, the relay switch contacts close allowing battery voltage to flow from the front fog lamp fuse to the front fog lamp control circuit which illuminates the front fog lamps. The left front fog lamp receives ground at G101 and the right front fog lamp is grounded at G102.

### Park, Tail, License and Marker Lamps

The headlamp switch is supplied with voltage from the instrument panel cluster (IPC) by two signal circuits, the AUTO lamps signal circuit and the PARK lamp signal circuit. When the headlamp switch is placed in the PARK position, the park lamp signal circuit is provided with ground through the switch contacts of the park lamp switch to a common headlamp switch ground back to the IPC. The IPC interprets the flow of voltage and responds by sending a serial data message to the underhood electrical center (UEC) and the rear electrical center (REC) requesting the front and rear park lamps be activated. The UEC and REC respond by applying voltage to there respective park, marker, and license lamp control circuits illuminating the park, marker and license lamps.

#### Curb Side Parking Lamps

Curb side parking lamps is a feature that allows the vehicles owner to activate either the left or right side parks lamps while the vehicle is parked and the ignition is off. Curb side parking lamps is a European mandate and all vehicles sold in the United States will be programmed with it. This feature is software driven and cannot be changed or reprogrammed to illuminate it. To activate the curb side parking lamps the following conditions must be met:

1. Ignition OFF.
2. Turn signal switch placed in either the RIGHT or LEFT position.

When these conditions are met, the front and rear parking lamps for only the side selected will remain illuminated until the turn signal switch is placed in the neutral position or the ignition switch is cycled ON then OFF. This feature is not safe guarded by the vehicles battery rundown protection and in the event that the curb side parking feature is left ON, total battery discharge will occur. Upon activating the curb side parking lamps, an audible warning of three chimes will notify the vehicles owner that the feature is active.

### Turn Signal Lamps

The turn signal switch is integrated into the steering column module. When the turn signal switch is activated, the steering column module interprets the position of the switch and sends a serial data message to the underhood electrical center (UEC) and the rear electrical center (REC) requesting either the right or left turn signals be activated. The UEC and REC respond by applying a pulsating voltage to the appropriate turn signal control circuits to illuminate the front and rear turn signal lamps. The steering column module also sends a serial data message to the instrument panel cluster (IPC) requesting the appropriate turn signal indicator be illuminated.

### Hazard Flasher Lamps

The hazard flashers may be activated in any power mode. The hazard switch is located on the accessory control panel and is permanently grounded through ground G205. When the hazard switch is placed in the ON position, ground is applied through the hazard switch signal circuit to the instrument panel cluster (IPC). The IPC responds by sending a serial data message to the underhood electrical center (UEC) and the rear electrical center (REC) requesting the front and rear turn signal lamps be illuminated in an ON and OFF duty cycle. The UEC and REC respond by applying voltage to there respective turn signal control circuits illuminating the front and rear turn signal lamps ON and OFF. The IPC is also responsible for cycling both turn signal indicators ON and OFF. The IPC illuminates the hazard switch telltale by applying voltage to the hazard switch telltale signal circuit.

### Stop Lamps

The brake pedal position sensor is used to sense the action of the driver application of the brake pedal. The brake pedal position sensor receives B+ voltage from the underhood electrical center (UEC) from the F16 fuse. When the brake pedal is applied, the brake pedal position sensor switch contacts close. With the switch contacts closed, B+ voltage flows through the brake pedal position sensor signal circuit to the rear electrical center (REC), electronic brake control module (EBCM), engine control module (ECM), shift lock solenoid, and transmission control module (TCM). The REC responds by applying voltage to the left and right stop/turn lamp control circuits as well as the center high mounted stop lamp (CHMSL) control circuit illuminating the brake lamps.

### Backup Lamps

#### Automatic Transmission

The park/neutral position switch receives voltage from the underhood electrical center (UEC) via the backup lamp switch signal circuit. When the transmission is placed in the REVERSE position, the park/neutral position switch closes providing a ground path for the backup lamp switch signal circuit. The UEC responds to the flow of voltage by sending a serial data message to the rear electrical center (REC) requesting the backup lamps be illuminated. The REC applies battery voltage to the backup lamps control circuit illuminating the backup lamps. Once the driver moves the gear selector out of the REVERSE position, a message is sent by the UEC via serial data requesting the REC to remove battery voltage from the backup lamps control circuit. The backup lamps are permanently grounded at G403.

#### Manual Transmission

The underhood electrical center (UEC) provides the normally open backup lamp switch with voltage. When the transmission is placed in the reverse position, the backup lamp switch closes providing a ground path through G104. The UEC responds to the flow of voltage by sending a serial data message to the rear electrical center (REC) requesting the backup lamps be illuminated. The REC applies battery voltage to the backup lamps control circuit illuminating the backup lamps. Once the driver moves the gear selector out of the REVERSE position, a message is sent by the UEC via serial data requesting the REC to remove battery voltage from the backup lamps control circuit. The backup lamps are permanently grounded at G403.