Exterior Lighting - System Operation and Component Description

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If a front or rear turn signal lamp is inoperative, the BCM fast flashes the remaining turn lamp(s) approximately 150 times per minute to indicate a bulb outage to the driver.

The LH steering column multifunction switch has 2 detents for the left turn position and 2 detents for the right turn position. When placed in the first detent and released, the corresponding turn signals flash 3 times and turn off. When the LH steering column multifunction switch is moved to the second detent, the turn signal flashes until the steering wheel is turned in the opposite direction.

The BCM Body Control Module (BCMB) and also provide an Field Effect Transistor (FET) protection of the stoplamp output circuits. When an excessive current draw is detected, the BCM or Body Control Module (BCMB) disable the affected stoplamp circuit driver.

Refer to: Module Controlled Functions - System Operation and Component Description (419-10 Multifunction Electronic Modules, Description and Operation).

Hazard Lamps

The BCM sends a voltage signal to the hazard flasher lamp switch (integrated into the FCIM) to monitor for a hazard lamp function request. When the hazard flasher lamp switch is pressed, the voltage signal is routed to ground, indicating a request to activate or deactivate the hazard lamp function.

When the BCM receives a request for the hazard lamps, it activates all the turn signal lamps.

The timed on/off cycle for the hazard lamps is approximately 70 times per minute, regardless of bulb outage.

Parking, Rear, and License Plate Lamps

System Diagram

Parking Lamps

The BCM monitors the headlamp switch position by sending voltage signals on multiple circuits to the headlamp switch. There is one circuit for each headlamp switch position. At any given time, one of the signal circuits is switched to ground to indicate the headlamp switch position.

If the BCM detects a fault from the headlamp switch or loses communication with the headlamp switch, the BCM turns the parking and headlamps on. This is normal behavior of the BCM when a fault has been detected with the inputs from the headlamp switch.

When the BCM receives an input requesting the parking lamps on, it provides voltage to the front parking, front, rear and rear side marker and license plate lamps.

The BCM supplies a high current switched voltage to the headlamp assemblies to supply the necessary current to operate the lamps and headlamp LED park/signature lamps and to the rear lamp assemblies to operate the parking lamp Light Emitting Diodes (LEDs). The BCM provides a low current voltage signal to the headlamp assemblies to switch on the LED signature lamps and to the rear lamp assemblies to switch on the parking lamp