B2578

DTC B2578

CIRCUIT DESCRIPTION
The body control module (BCM) controls the headlamp relay by grounding the control circuit of the headlamp relay coil.

CONDITIONS FOR RUNNING THE DTC
- Voltage supplied to the module is in the normal operating voltage range (approximately 10-16 volts).
- The headlamps must be ON.

CONDITIONS FOR SETTING THE DTC
- The BCM detects a short to voltage in the headlamp relay control circuit or the low beam headlamp relay control circuit when the BCM energizes the headlamp relay.
- The condition must be present for more than 3 ms.

ACTION TAKEN WHEN THE DTC SETS
- The BCM stores DTC B2578 in memory.
- The SERVICE VEHICLE SOON telltale illuminates.
- The BCM activates the daytime running lamps.

CONDITIONS FOR CLEARING THE DTC
- A current DTC B2578 clears if the BCM no longer detects a short to battery positive voltage in the low beam headlamp relay control circuit or the headlamp relay control circuit.
- A history DTC B2578 clears after 100 consecutive ignition cycles.
- The BCM receives the clear code commend from the scan tool.

DIAGNOSTIC AIDS
- If the DTC B2578 is a history DTC, the fault may be intermittent.
- An intermittent short to voltage in the following locations may cause an intermittent malfunction to occur:
- The headlamp relay control circuit
- The headlamp relay
- The BCM

TEST

Steps 1-5:

Steps 6-11:

Steps 12-13: