Backlight Dimming Rx Failure (Active)

BACKLIGHT DIMMING RX FAILURE (ACTIVE)

For a complete wiring diagram Consult Diagrams/Electrical

- When Monitored:
With the ignition on.

- Set Condition:
If the A/C - Heater Control Module does not receive the dimming function message from the Body Control Module for more than 5 seconds, then the A/C - Heater Control Module backlighting will default to full brightness and the DTC will set.





Diagnostic Test

1. DIMMING MESSAGE NOT SEEN AT RATE EXPECTED

NOTE: Make sure that the Panel Dimmer switch is not in set in Funeral Mode.

Turn the ignition on.
Turn the Blower control to low speed.
Press the A/C switch on.
Press the EBL switch on.
Watch the A/C and EBL status indicators on the A/C-Heater Control Module while turning the Headlamp switch on and then off.
Did the status indicators dim when the Headlamp switch was turned on?

Yes

- No problem found at this time.
- Perform BODY VERIFICATION TEST - VER 1. Body Verification Test.

No

- Go To2

2. A/C HEATER CONTROL MODULE
Turn the ignition on.
With the scan tool Monitor Display, PCI Bus Messages, look for the VF DIM Msg Present.
Does the scan tool display: VF DIM Msg present: Yes?

Yes

- Replace the A/C - Heater Control Module.
- Perform BODY VERIFICATION TEST - VER 1. Body Verification Test.

No

- Replace the Body Control Module.
- Perform BODY VERIFICATION TEST - VER 1. Body Verification Test.