Code B122: Panel Dimming Potentiometer Circuit: Notes

The panel dimmer is a potentiometer that indicates desired display intensity to BCM. The BCM supplies voltage on circuit No. 705 and a ground on circuit No. 736 to potentiometer in left switch assembly. The wiper provides voltage signal to BCM on circuit No. 686, indicating position of slider and delay time. When slider is moved toward minimum position, its resistance increases and signal voltage decreases.

Code B122 will set, if signal voltage indicates less than 2 percent (open or grounded circuit), or greater than 98 percent (shorted to voltage). During time failure is present, a substitute delay time will be implemented to allow continued operation of interior lighting. The reading from potentiometer BD42 display will indicate actual reading.

NOTE: Test numbers refer to numbers on diagnostic chart.

Test Number 1) Checks to see if open or grounded circuit reading is due to circuits or switch assembly. If open or grounded circuit reading changes to a short to voltage reading, after jumpering switch assembly terminals, BCM and wiring are okay.

Test Number 2) Measuring voltage between circuit No. 705 (5 volts) and circuit No. 736 will determine if problem is in circuits No. 705 or 686.

Test Number 3) Checks to see if short to voltage circuit reading is due to circuit or an open in circuit No. 736 and switch assembly. If a short to voltage reading changes to an open circuit reading, after disconnecting switch assembly, BCM and circuit No. 686 are okay.