Lighting System Diagnosis

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

CONDITIONS FOR RUNNING THE DTC
A short to ground is tested for under the following conditions:
^ The Ignition is ON.
^ The PARK LAMPS relay is de-energized.
^ DTC B1970 is not current.

A short to battery is tested for under the following conditions:
^ The Ignition ON.
^ The PARK LAMPS relay is energized.
^ DTC B1970 is not current.

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

ACTION TAKEN WHEN THE DTC SETS
The BCM turns OFF the PARK LAMPS 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 PARK LAMPS relay is no longer low for at least 3 seconds.
^ The BCM detects that the control circuit of the PARK LAMPS relay is no longer high for at least 3 seconds.

TEST DESCRIPTION

Step 1-4:

Step 5-15:

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