Theory Of Operation

When the ignition is on, the Body Control Module (BCM) provides a 12-volt signal, on the Left and Right Lighting Fault Sense circuits, to the Left and Right Front Lamp Assemblies, and the Left and Right Tail Lamp Assemblies. When the Left or Right Turn Lamp is activated, the Body Control Module (BCM) provides a 12-volt signal on the Left or Right Front Turn Lamp Driver circuit, or the Left or Right Rear Turn Lamp Driver circuit, indicating the Turn Lamps have been requested.

When the Left or Right Turn Lamp is activated, an internal driver in the Front and Tail Lamp Assemblies pulls the Lighting Fault Sense circuit voltage signal low (below 6 volts), in sequence with the Turn Lamp flash. When the Turn Lamps are Off, the BCM maintains the Lighting Fault Sense circuit voltage signal high (above 8 volts).

A failure in the Lighting Fault Sense circuit may be caused by one of the following conditions:

• When the Left or Right Turn Lamps are ON, and the voltage on the Lighting Fault Sense circuit is constantly 12 volts (system voltage), may indicate the Lighting Fault Sense circuit is open or shorted to voltage, the Ground circuit is open, a poor connection or an inoperative Lamp Assembly.
• When the Left or Right Turn Lamps are OFF, the Lamp Assembly is not disconnected and the voltage on the Lighting Fault Sense circuit is below 6 volts, may indicate a short to ground on the Lighting Fault Sense circuit, an internally shorted Lamp Assembly, or water/corrosion at a harness connector/terminal.
• When a Lamp Assembly is disconnected, the Lighting Fault Sense circuit is not shorted to ground, and the voltage on the Lighting Fault Sense circuit is below 6 volts, may indicate the BCM is not supplying the 12-volt signal on the Lighting Fault Sense circuit.