Diagnostic Aids
- If the DTC B2578 is a history DTC, the fault may be intermittent. Refer to TESTING WIRING SYSTEMS FOR INTERMITTENT & POOR CONNECTIONS .
- The following conditions may cause an intermittent malfunction to occur:
- An intermittent short to battery in the headlamp relay coil control circuit.
- The headlamp relay coil is intermittently shorted to battery.
- The BCM is intermittently shorted to battery.