B2577

CIRCUIT DESCRIPTION
The Body Control Module (BCM) controls the headlamp relay. The BCM grounds the headlamp relay control circuit which energizes the headlamp relay.

CONDITIONS FOR RUNNING THE DTC
The BCM must not be commanding the headlamp relay to energize.

CONDITIONS FOR SETTING THE DTC
^ The BCM detects a short to ground or open in the headlamp relay control circuit when the BCM is not trying to energize the headlamp relay.
^ The condition above must be present for more than 0.3 seconds.

ACTION TAKEN WHEN THE DTC SETS
The BCM stores DTC B2577 in memory.

CONDITIONS FOR CLEARING THE DTC
^ A current DTC B2577 will clear if the BCM no longer detects a short to ground or open in the headlamp relay control circuit.
^ A history DTC B2577 will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present.
^ The BCM receives a clear code command from the scan tool.

DIAGNOSTIC AIDS
^ If the DTC B2577 is a history DTC, the fault may be intermittent. Refer to Testing for Intermittent and Poor Connections in Diagrams.
^ The following conditions may cause an intermittent malfunction to occur:
- An intermittent short to ground or open in the headlamp relay control circuit.
- The headlamp relay coil is intermittently shorted to ground or open.
- The BCM is intermittently shorted to ground or open.

TEST DESCRIPTION

Steps 1-6:

Steps 7-15:

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.
4. Tests for voltage at the coil side feed of the headlamp relay. The LP Park fuse supplies power to the coil side feed of the headlamp relay.
5. Verifies that the BCM is providing ground to the headlamp relay.
6. Tests if ground is constantly being applied to the headlamp relay.