Interior Backlighting Does Not Dim

WARNING: This page is about a different car, the 2004 Cadillac CTS. However, it is still accessible from the selected car via links, so may be relevant.

Step	Action	Yes	No
Schematic Reference: Interior Lights Dimming Schematics Connector End View Reference: Master Electrical Component List in Wiring Systems
1	Did you perform the Lighting Systems Diagnostic System Check?	Go to Step 2	Go to Diagnostic System Check - Lighting Systems
2	Turn ON the ignition, with the engine OFF. Place the headlamp switch in the PARK position. Cover the sunload sensor. Turn the instrument panel (I/P) lamps dimmer switch from minimum to maximum intensity. Do the interior backlighting lamps operate properly?	Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems	Go to Step 3
3	Are all of the interior backlighting lamps always ON?	Go to Step 4	Go to Step 9
4	Install a scan tool. With a scan tool, observe the Dimming Potentiometer parameter in the Dash Integration Module (DIM) Inputs data list. Move the I/P lamps dimmer switch from minimum to maximum intensity. Does the scan tool indicate that the Dimming Potentiometer parameter is changing when the I/P lamps dimmer switch is moved?	Go to Step 5	Go to Step 7
5	With a scan tool, observe the Park Lamp Switch status in the DIM Inputs data list. Does the scan tool display ON?	Go to Step 6	Go to Step 8
6	With a scan tool, observe the Photocell Status parameter in the Climate Control Panel (CCP) Lighting Data list. Does the scan tool display DARK?	Go to Step 11	Go to Twilight Sentinel Inoperative
7	Test the I/P lamps dimmer switch signal circuit for an short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 15	Go to Step 10
8	Test the park lamp relay control circuit for an open circuit or a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 15	Go to Step 11
9	Inspect for poor connections at the harness connector of the appropriate controlling module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 15	Go to Step 12
10	Inspect for poor connections at the harness connector of the I/P lamps dimmer switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 15	Go to Step 13
11	Inspect for poor connections at the harness connector of the DIM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 15	Go to Step 14
12	IMPORTANT: Perform the setup procedure for the appropriate module. Replace the appropriate controlling module. Refer to Dash Integration Module Replacement in Body Control System and Door Control Module Replacement in Doors.Did you complete the replacement?	Go to Step 15	-
13	Replace the I/P lamps dimmer switch. Refer to Instrument Panel (I/P) Dimmer Switch Replacement . Did you complete the replacement?	Go to Step 15	-
14	IMPORTANT: Perform the setup procedure for the DIM. Replace the DIM. Refer to Dash Integration Module Replacement in Body Control System.Did you complete the replacement?	Go to Step 15	-
15	Operate the system in order to verify the repair. Did you correct the condition?	System OK	Go to Step 2