Backlight Dimming RX Failure

BACKLIGHT DIMMING RX FAILURE

WHEN MONITORED
With the ignition on.

SET CONDITION
The Cluster broadcasts the VF Dim message on the PCI Bus. This DTC will set and the backlighting will default to full brightness if the A/C Heater Control does not receive this message for more than 5 seconds.

POSSIBLE CAUSES
- Faults present in the cluster (MIC)
- A/C heater control not receiving VF DIM message at the expected rate
- Cluster not broadcasting VF DIM message
- A/C heater control not receiving VF DIM message

Diagnostic Test

1. VERIFY THAT THE BACKLIGHT DIMMING RX FAILURE DTC IS ACTIVE
Turn the ignition on.
With the DRBIII(R), erase HVAC DTCs.
Cycle the ignition switch and wait approximately 30 seconds.
With the DRBIII(R), read active HVAC DTCs.

Q: Does the DRBIII(R) display: Backlight Dimming RX Failure?

YES: Go To 2
NO: A technician may not have erased this DTC following a module or PCI Bus repair. If possible, verify if the vehicle was recently in for this type of service. Otherwise, visually inspect the related wiring harness for chafed, pierced, pinched, and partially broken wires and the wiring harness connectors for broken, bent, pushed out, and corroded terminals. Repair as necessary. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test

2. CHECK FOR DTCs IN THE CLUSTER (MIC)
Turn the ignition on.
With the DRBIII(R), read Cluster DTCs.

Q: Does the DRBIII(R) display any DTCs?

YES: Diagnose and repair the DTC(s). Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
NO: Go To 3

3. CHECK BACKLIGHT DIMMING FUNCTION
Turn the Headlamp switch on.
Turn the Blower control to low speed.
If equipped, press the A/C mode switch on.
If equipped, press the EBL mode switch on.
If equipped, press the Max mode switch on.
Rotate the Cargo Dome switch in both directions while watching the A/C status indicator (if equipped), the EBL status indicator (if equipped), and the MAX status indicator (if equipped) on the A/C Heater Control.

Q: Do the status indicators dim and brighten with respect to the position of the Cargo Dome switch?

YES: No problem found at this time. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
NO: Go To 4

4. VERIFY THAT THE CLUSTER IS BROADCASTING THE VF DIM MESSAGE ON THE PCI BUS
With the DRBIII(R) in HVAC, select Monitor Display and then select PCI Bus Messages.
From the list, select VF DIM Msg Present.

Q: Does the DRBIII(R) display: VF DIM Msg Present: YES?

YES: Replace the A/C Heater Control. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
NO: Replace the Cluster. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test