Headlight Switch Input Circuit Low

Monitored & Set Condition

When Monitored: With ignition On.
Set Condition: The BCM detects a voltage less than .25-volts on the Headlamp Switch Input for more than 5 seconds.

Possible Causes:

Intermittent Condition
Headlamp Switch Shorted
Headlamp Switch MUX Circuit Short To Return Circuit
Headlamp Switch Return Circuit Short To Ground
Headlamp Switch Return Circuit Short To Ground
Body Control Module

Testing

Turn the ignition on. With the DRBIII(R), clear all BCM DTC's. Turn the headlamps to the ON position. With the DRBIII(R), read DTCs. Does the DRBIII(R) display: HEADLAMP SWITCH INPUT CKT LOW? If yes, go to next step. If no, the condition that caused the symptom is currently not present. Inspect the related wiring for a possible intermittent condition. Look for any chafed, pierced, pinched, or partially broken wires. Perform BODY VERIFICATION TEST .
Turn the ignition off. Disconnect the Headlamp Switch harness connector. Turn the ignition on. With the DRBIII(R), select Body, Body Control Module and read: Headlamp Switch Voltage. Does the DRBIII(R) display Headlamp Switch voltage above 4.8 volts? If yes, replace the Headlamp Switch. Perform BODY VERIFICATION TEST . If no, go to next step.
Turn the ignition off. Disconnect the Body Control Module harness connector. Disconnect the Headlamp Switch harness connector. Measure resistance between the Headlamp Switch Return circuit and the Headlamp Switch MUX circuit. Is the resistance below 5.0 ohms? If yes, repair the Headlamp Switch MUX circuit for a short to the Headlamp Switch Return circuit. Perform BODY VERIFICATION TEST . If no, go to next step.
Measure resistance between ground and the Headlamp Switch MUX circuit. Is the resistance above 5.0 ohms? If yes, repair the Headlamp Switch MUX Circuit for a short to ground condition. Perform BODY VERIFICATION TEST . If no, go to next step.
Measure resistance between ground and the Headlamp Switch Return circuit. Is the resistance below 5.0 ohms? If yes, repair the Headlamp Switch Return Circuit for a short to ground condition. Perform BODY VERIFICATION TEST . If no, replace the Body Control Module. Perform BODY VERIFICATION TEST .