BCM Code B123, Courtesy Light Switch Circuit: Notes

The courtesy lights panel switch is part of dimmer control potentiometer. In left switch assembly, the COURTESY LIGHTS ENABLE switch closes when dimmer is moved to extreme right. The BCM supplies signal voltage on circuit No. 685, which is pulled to ground through circuit No. 736 when switch contact is closed.

Code B123 will set when ignition is on, dimming potentiometer is working properly (Code B122) and signal voltage is high when dimmer is moved to enable position or signal voltage is low when dimmer is moved to maximum dim position.

1. BCM input parameter B101 displays voltage state of circuit No. 685 at BCM.
2. Check to see if open circuit reading is caused by circuit or switch assembly. If display changes from HI to LO when switch terminals are jumped together, BCM and wiring are okay.
3. Check to see if open circuit reading is caused by BCM or wiring.
4. With courtesy lights switch off, checks if short to ground reading is due to switch assembly or wiring.