B2577
DTC B2577
Circuit Description
The body control module (BCM) controls the headlamp relay by grounding the control circuit of the headlamp.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC B2577 Headlamp Control Circuit Low
Conditions for Running the DTC
Voltage supplied to the module is in the normal operating voltage range, approximately 9-16 volts.
Conditions for Setting the DTC
* The BCM detects a short to ground or an open in the control circuit of the headlamp relay coil or the low beam headlamp control circuit relay when the BCM is not energizing the headlamp relay.
* The condition is present for more than 3 ms.
Action Taken When the DTC Sets
* The BCM stores DTC B2577 in memory.
* The SERVICE VEHICLE SOON telltale illuminates.
* With the ignition in the RUN position, the BCM deactivates the daytime running lamps and turns on the park lamps.
Conditions for Clearing the DTC
* A current DTC B2577 clears if the BCM no longer detects a short to ground or an open in the control circuit of the headlamp relay control circuit of the low beam relay headlamp control circuit.
* A history DTC B2577 clears after 100 consecutive ignition cycles.
* The BCM receives the Clear Code commend from the scan tool.
Diagnostic Aids
* If the DTC B2577 is a history DTC, the fault may be intermittent. Refer to Testing for Intermittent Conditions and Poor Connections. Component Tests and General Diagnostics
* An intermittent short to ground or an open in the following locations may cause an intermittent malfunction to occur:
- The low beam headlamp relay control circuit
- The headlamp relay control circuit
- The headlamp relay
- The BCM
TEST
