B122 - Twilight Delay & Panel Dimming

BCM Code B120-B122:

Headlight Circuit:

CIRCUIT DESCRIPTION:
Since both potentiometers use the same power and ground, chances are that the problem is in the power or ground circuits when both codes are stored.

TEST DESCRIPTION: Test numbers refer to circled numbers on the diagnostic chart.

1. BCM data value BD43 displays a twilight delay value. The normal range is between 4 and 96%.
2. Check to see if the open or grounded circuit reading is due to the circuit or the switch assembly. If voltage can be read across CKTs 705 & 736 after disconnecting the switch assembly, the BCM and wiring are OK.
3. Check for 5 volt reference at the switch. If 5 volts is present, CKT 736 is open. If CKT 736 is open, the open will be between terminal "A3" on left switch assembly and cavity G3 on dash - IP transition connector.
4. If CKT 705 is suspected of being grounded, remove the HVAC programmer and BCM connectors prior to making a ground check.
5. If there is no ground in CKT 705 replace HVAC programmer or BCM.

NOTES ON INTERMITTENTS:
If an intermittent Codes B120 & B122 are being set, manipulate the related wiring while observing either BCM data VALUE BD42 and/or BD43. If the failure is induced, the reading will jump from its normal value to a reading outside of its range (refer to specific charts for range).