Auto Headlamp Signal Circuit Open

Tests 1 - 2:

Tests 3 - 4:

SYMPTOM
AUTO HEADLAMP SIGNAL CIRCUIT OPEN

WHEN MONITORED :
When Headlamp Switch is in the AUTO position.

SET CONDITION:
During the first 2 seconds of each ignition ON cycle the rear view mirror will ground the BCM's input circuit. If the BCM does not receive this ground, it will always turn the headlamp on in the AUTO position.

POSSIBLE CAUSES
- Auto headlamp signal circuit open
- Auto headlamp signal circuit shorted to ground
- Electrochromic mirror defective - sensor stuck on (default)
- BCM Defective - Auto headlamp sensor stuck on