B2578

B2578 - Headlamp Control Circuit High

Schematic:

CIRCUIT DESCRIPTION
The Body control module (BCM) activates the headlamp relay when the light sensor senses a dark condition. Battery voltage is supplied to the headlamp relay through the BACK/UP fuse locate in the UHFB. The BCM provides ground to circuit 352 to activate the headlamp relay; if the headlamp relay control circuit is shorted to battery for one second DTC B2578 will fail as current.

DTC PARAMETERS
- Headlamp relay is commanded On.
- Short to Battery.
- Ignition in RUN.
- Condition is present for 1 seconds.
- No telltale will illumination.

DIAGNOSTIC AIDS
- Check for poor connection at the BCM. Inspect harness connectors for backed-out terminals, improper terminal mating, broken connector locks, improperly formed or damaged terminals and poor terminal-to-wire connection (terminal crimped over wire insulation and not conductors).
- Inspect wiring harness for damage. Check for broken or chaffed insulation.
- If fault is suspected to be intermittent, wiggling harness wiring may help in locating fault.

TEST

Diagnostic Chart: