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 BACKUP/TURN 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.
Conditions for Setting the DTC
| • | The headlamp relay is commanded ON. |
| • | The condition is present for 1 second. |
| • | No light will illuminate in the instrument panel (I/P). |
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 the wiring harness for damage. Inspect for broken or chaffed insulation. |
| • | If fault is suspected to be intermittent, wiggling the harness wiring
may help in locating fault. |
