Principles Of Operation

Daytime Running Lamps (DRL)

Principles of Operation

The Body Control Module (BCM) controls the Daytime Running Lamps (DRL) by energizing the DRL relay when the ignition is in RUN and the headlamp switch is not in the HEADLAMPS ON position.

When the DRL relay is energized, voltage is routed through a resistor wire to the low beam relay. The voltage passes through the low beam relay to the existing circuitry for the low beams. The voltage passes through a resistor wire to illuminate the low beams at reduced intensity.

The DRL is not a programmable parameter for this vehicle.

Field-Effect Transistor (FET) Protection

A Field-Effect Transistor (FET) is a type of transistor that, when used with module software, monitors and controls current flow on module outputs. The FET protection strategy prevents module damage in the event of excessive current flow.

The BCM utilizes a FET protective circuit strategy for many of its outputs (such as a turn lamp output circuit). Output loads (current level) are monitored for excessive current (typically short circuits) and are shut down when a fault event is detected. A short circuit DTC sets when the fault event occurs.

The circuit remains off until the fault is corrected and the ignition is cycled off and then back on, the module resets the FET protection and allows the circuit to function.

The FET protected circuit for the DRL system is the DRL relay coil ground circuit.