Conditions for Setting the DTC

WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2003 GMC Savana Special, 2003 GMC Savana Camper Special, 2003 GMC Savana, 2003 Chevrolet RV Cutaway, and 2003 Chevrolet Cutaway. However, it is still accessible from the selected car via links, so may be relevant.

When the low beam headlamp relay control circuit is open or shorted to ground.
When the BCM receives a low beam headlamp ON command and the low beam headlamp relay control circuit is shorted to voltage.
When the low beam relay coil side is open or the battery positive voltage to the low beam relay is open.