Principles Of Operation

Turn Signal and Hazard Lamps

Principles of Operation

The Steering Column Control Module (SCCM) monitors the multifunction switch position. When the multifunction switch is in the LH or RH TURN position, the SCCM (Steering Column Control Module) sends a message over the High Speed Controller Area Network (HS-CAN) to the Body Control Module (BCM) indicating a request for the LH or RH turn signal.

The BCM (Body Control Module) sends a voltage signal to the Front Controls Interface Module (FCIM) to monitor for a hazard lamp function request. When the hazard flasher switch (a capacitive touch switch) is touched, the voltage signal is routed to ground, indicating a request to activate or deactivate the hazard lamp function.

When the BCM (Body Control Module) receives a request for a turn signal or the hazard lamps, the BCM (Body Control Module) supplies on/off voltage to the appropriate turn lamps.

The timed on/off cycle for turn lamps is determined by the BCM (Body Control Module) and is set to flash approximately 80 times per minute if both the front and rear turn signal lamps operate correctly. If a front or rear turn signal lamp is inoperative, the BCM (Body Control Module) fast flashes the remaining turn lamp approximately 160 times per minute to indicate a bulb outage to the driver.

The timed on/off cycle for the hazard lamps is approximately 80 times per minute regardless of bulb outage.

For MKX, the rear turn signal lamps share functionality with the rear stoplamps.

The multifunction switch is a momentary contact switch, with 2 detents for the LH turn position and 2 detents for the RH turn position. When placed in the first detent and released, the corresponding turn signals flash 3 times and turn off. When the multifunction switch is moved to the second detent and released, the turn signal flashes until the steering wheel is turned in the opposite direction (based on input from the steering wheel rotation sensor), the multifunction switch is moved to the second detent a second time or the vehicle travels farther than 3.2 km (2 miles). The BCM (Body Control Module) monitors the steering wheel rotation sensor and the multifunction switch input to determine when to cancel the turn signals. The BCM (Body Control Module) monitors the distance traveled to determine if the turn signal should be turned off.

Field-Effect Transistor (FET) Protection

The Field-Effect Transistor (FET) protection strategy prevents module damage in the event of excessive current flow. For additional information of the FET (Field-Effect Transistor), refer to Body Control Systems.

The BCM (Body Control Module) FET (Field-Effect Transistor) protected output circuits for the turn lamp system are the LH and RH front and rear turn lamp output circuits.