Headlamp Switch Input Circuit Low
HEADLAMP SWITCH INPUT CIRCUIT LOWWHEN MONITORED
Ignition on.
SET CONDITION
BCM detects a voltage less than 0.25 volts on the Headlamp Switch Input for more than 5 seconds.
POSSIBLE CAUSES
- Headlamp switch shorted
- Headlamp switch mux circuit short to return circuit
- Headlamp switch mux circuit short to ground
- Headlamp switch return circuit short to ground
- Body control module
DIAGNOSTIC TEST
1. INTERMITTENT CONDITION
Turn the ignition on.
With the Scan Tool, clear all BCM DTC's.
Turn the headlamps to the ON position.
With the Scan Tool, read DTCs.
Q: Does the Scan Tool display: HEADLAMP SWITCH INPUT CKT LOW?
YES: Go To 2
NO: The condition is not present at this time. Monitor Scan Tool parameters while wiggling the related wire harness. Refer to any Technical Service Bulletins that may apply. Visually inspect the related wiring harness and connector terminals.
Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
2. HEADLAMP SWITCH SHORTED
Turn the ignition off.
Disconnect the Multifunction Switch harness connector.
Turn the ignition on.
With the Scan Tool, select Body, Body Control Module and read: Headlamp Switch voltage.
Q: Does the Scan Tool display Headlamp Switch voltage above 4.8 volts?
YES: Replace the Multifunction Switch.
Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
NO: Go To 3
3. HEADLAMP SWITCH MUX CIRCUIT SHORT TO MUX RETURN CIRCUIT
Turn the ignition off.
Disconnect the Body Control Module harness connector.
Disconnect the Multifunction Switch harness connector.
Measure resistance between the Headlamp Switch Return circuit and the Headlamp Switch MUX circuit.
Q: Is the resistance below 5.0 ohms?
YES: Repair the Headlamp Switch MUX circuit for a short to the Headlamp Switch Return circuit.
Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
NO: Go To 4
4. HEADLAMP SWITCH MUX CIRCUIT SHORT TO GROUND
Turn the ignition off.
Disconnect the Body Control Module harness connector.
Disconnect the Multifunction Switch harness connector.
Measure resistance between ground and the Headlamp Switch MUX circuit.
Q: Is the resistance above 5.0 ohms?
YES: Repair the Headlamp Switch MUX Circuit for a short to ground condition.
Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
NO: Go To 5
5. HEADLAMP SWITCH RETURN CIRCUIT SHORT TO GROUND
Turn the ignition off.
Disconnect the Body Control Module harness connector.
Disconnect the Multifunction Switch harness connector.
Measure resistance between ground and the Headlamp Switch Return circuit.
Q: Is the resistance below 5.0 ohms?
YES: Repair the Headlamp Switch Return Circuit for a short to ground condition.
Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
NO: Replace the Body Control Module.
Perform BODY VERIFICATION TEST - VER 1. Body Verification Test