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 headlamp switch park lamps on signal circuit is open or has a high resistance.
When the headlamp switch headlamps on signal circuit is shorted to ground.