Dodge Ram 2004, Service Manual

Page: 388 / 642

Symptom:
BACKLIGHT DIMMING RX FAILURE (ACTIVE)
When Monitored and Set Condition:
BACKLIGHT DIMMING RX FAILURE (ACTIVE)
When Monitored: With the ignition on.
Set Condition: If the A/C - Heater Control Module does not receive the dimming function
message from the Instrument Cluster for more than 5 seconds, then the A/C - Heater
Control Module backlighting will default to full brightness and the DTC will set.
POSSIBLE CAUSES
CHECK FOR INSTRUMENT CLUSTER (MIC) DTCS
DIMMING MESSAGE NOT SEEN AT RATE EXPECTED
A/C - HEATER CONTROL MODULE
MIC - NO DIM MESSAGE TO A/C - HEATER CONTROL MODULE
TEST ACTION APPLICABILITY
1 Turn the ignition on.
With the DRBIII
t
in Body, Electro/Mech Cluster (MIC), read DTCs.
Does the DRBIII
t
display any DTCs?
All
Yes
→
Refer to the Instrument Cluster category for the related symp-
tom(s).
Perform BODY VERIFICATION TEST - VER 1.
No
→
Go To 2
2 Turn the ignition on.
Turn the Headlamp switch on.
Turn the Blower control to low speed.
If equipped, press the A/C switch on.
If equipped, press the EBL switch on.
If equipped, press the Max switch on.
Rotate the Cargo Dome switch in both directions while watching the A/C (if
equipped), EBL (if equipped), and MAX (if equipped) status indicators on the
A/C-Heater Control Module.
Do the status indicators dim and brighten respectively while rotating the switch? All
Yes
→
No problem found at this time.
Perform BODY VERIFICATION TEST - VER 1.
No
→
Go To 3
374
HEATING & A/C