B2472

CIRCUIT DESCRIPTION
The Body Control Module (BCM) supplies battery positive voltage to the HEADLAMP relay coil. The BCM provides ground to the HEADLAMP relay in the control circuit. The BCM monitors the voltage in the HEADLAMP relay control circuit every second.

CONDITIONS FOR RUNNING THE DTC
A short to ground in the control circuit of the HEADLAMP relay will be tested when the following conditions are met:
^ The ignition is ON.
^ The HEADLAMP relay is de-energized.
^ The headlamp switch is in the OFF position.
^ DTC B1970 is not present.

A short to battery positive voltage in the control circuit of the HEADLAMP relay will be tested when the following conditions are met:
^ The ignition is ON.
^ The HEADLAMP relay is energized.
^ DTC B1970 is not present.

CONDITIONS FOR SETTING THE DTC
One of the following conditions will cause this DTC to set:
^ The HEADLAMP relay is de-energized, and the BCM detects that the voltage in the control circuit of the HEADLAMP relay is low for at least 3 seconds.
^ The HEADLAMP relay is energized, and the BCM detects that the control circuit of the HEADLAMP relay is high for at least 3 seconds.

ACTION TAKEN WHEN THE DTC SETS
The BCM turns OFF the HEADLAMP relay output, until the condition for setting the DTC is no longer present.

CONDITIONS FOR CLEARING THE DTC
The DTC will clear when the following conditions are met:
^ The BCM detects that the voltage in the control circuit of the HEADLAMP relay is no longer low for at least 3 seconds.
^ The BCM detects that the control circuit of the HEADLAMP relay is no longer high for at least 3 seconds.

TEST DESCRIPTION

Steps 1-3:

Steps 4-15:

The numbers below refer to the step numbers on the diagnostic table.
2. Listen for an audible click when the HEADLAMP relay operates. Command both the ON and OFF states. Repeat the commands as necessary.
3. Tests for voltage at the coil side of the HEADLAMP relay. The BCM supplies power to the coil side of the HEADLAMP relay through the headlamp relay coil supply voltage circuit.
4. Verifies that the BCM is providing ground to the HEADLAMP relay.
5. Tests if ground is constantly being applied to the HEADLAMP relay.