Interior Backlighting Malfunction
Interior Backlighting Malfunction
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.
Diagnostic Fault Information
Circuit/System Description
The instrument panel (I/P) dimmer switch is used to increase and decrease the brightness of the interior backlighting components. The I/P dimmer switch provides a voltage signal to the body control module (BCM) that will increase as the brightness of the lights are increased and decrease as the brightness of the lights are decreased. The BCM provides a low reference, signal, and a B+ circuit to the I/P dimmer switch. When the I/P dimmer switch is placed in the desired position, the dimmed voltage setting is applied from the I/P dimmer switch through the I/P dimmer switch signal circuit to the BCM. The BCM interprets the signal and applies a pulse width modulated (PWM) voltage through the light emitting diode (LED) dimming 1 and dimming 2 control circuits as well as the switch indictor LED control circuit illuminating the interior backlighting and switch indicator LED's to the requested level of brightness.
Reference Information
Schematic Reference
Interior Lights Dimming Schematics Interior Lights Dimming Schematics
Connector End View Reference
Component Connector End Views Fuel Pump and Level Sensor Assembly
Description and Operation
Interior Lighting Systems Description and Operation Interior Lighting Systems
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
Scan Tool Reference
Control Module References Control Module References for scan tool information
Circuit/System Verification
1. Ignition ON.
2. Verify the scan tool LED Backlight Dimming Command parameter changes between a high percentage to a low percentage while operating the dimmer switch from high to low.
• If the parameter does not change
Refer to Dimmer Switch Malfunction.
• If the parameter changes
3. Verify the switch indictor LED's for the components listed below turn ON and OFF while commanding the LED Backlight Dimming ON and OFF with a scan tool.
* S48C multifunction switch 1 - instrument panel
* S48D multifunction switch 2 - instrument panel
* S32LR seat heating switch - left rear
* S32RR seat heating switch - right rear
• If the switch indicator LED's do not turn ON and OFF
Refer to Switch Indicator LED Backlighting Malfunction.
• If the switch indicator LED's turn ON and OFF
4. Verify all backlighting components turn ON and OFF while commanding the LED Backlight Dimming ON and OFF with a scan tool.
• If all backlighting components do not turn ON and OFF
Refer to Interior Backlighting Malfunction.
• If all backlighting components turn ON and OFF
5. All OK.
Circuit/System Testing
Dimmer Switch Malfunction
1. Ignition OFF, disconnect the harness connector at the S36 instrument panel dimmer switch.
2. Verify a test lamp illuminates between the low reference circuit terminal 1 and B+.
• If the test lamp does not illuminate
1. Ignition OFF, disconnect the X1 harness connector at the K9 body control module.
2. Test for less than 2 ohms in the low reference circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the K9 body control module.
• If the test lamp illuminates
3. Ignition ON.
4. Verify a test lamp illuminates between the B+ reference circuit terminal 6 and ground.
• If the test lamp does not illuminate
1. Ignition OFF, disconnect the X1 harness connector at the K9 body control module.
2. Test for infinite resistance between the B+ reference circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance
3. Test for less than 2 ohms in the B+ reference circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the K9 body control module.
• If the test lamp illuminates
5. Verify the scan tool LED Backlight Dimming Command parameter is greater than 40%.
• If 40% or less
1. Ignition OFF, disconnect the X2 harness connector at the K9 body control module, ignition ON.
2. Test for less than 1 V between the signal circuit terminal 2 and ground.
• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V, replace the K9 body control module.
• If greater than 40%
6. Install a 3 A fused jumper wire between the signal circuit terminal 2 and the B+ circuit terminal 6.
7. Verify the scan tool LED Backlight Dimming Command parameter is less than 30%.
• If 30% or greater
1. Ignition OFF, disconnect the X2 harness connector at the K9 body control module.
2. Test for infinite resistance between the signal circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance
3. Test for less than 2 ohms in the signal circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the K9 body control module.
• If less than 30%
8. Test or replace the S36 instrument panel dimmer switch.
Interior Backlighting Malfunction
Note: Each component with backlighting may need to be disconnected to isolate a short to voltage or short to ground. Use the schematics to identify the following:
* Backlighting components the vehicle is equipped with
* Each component's control and ground circuit terminals
* Component locations on the backlighting control circuit
1. Ignition OFF, scan tool disconnected, all doors closed, all accessories OFF, disconnect the harness connector at the component with inoperative backlighting. It may take up to 2 minutes for all vehicle systems to power down.
2. Test for less than 5 ohms between the appropriate ground circuit terminal listed below and ground.
* S36 instrument panel dimmer switch terminal 4
* S12 dome lamp switch terminal 1
* E37LF dome/reading lamps - left front terminal 6
* E37LR dome/reading lamps - left rear terminal 6
* E37RF dome/reading lamps - right front terminal 6
* E37RR dome/reading lamps - right rear terminal 6
* S48C multifunction switch 1 - instrument panel terminal 5
* S48D multifunction switch 2 - instrument panel terminal 5
* S32LR seat heating switch - left rear terminal 3
* S32LR seat heating switch - right rear terminal 3
* S79LR window switch - left rear terminal 1
* S79RR window switch - right rear terminal 1
• If 5 ohms or greater
1. Ignition OFF.
2. Test for less than 2 ohms in the ground circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, repair the open/high resistance in the ground connection.
• If less than 5 ohms
3. Connect a test lamp between the appropriate control circuit terminal listed below and ground.
* S36 instrument panel dimmer switch terminal 5
* S12 dome lamp switch terminal 4
* E37LF dome/reading lamps - left front terminal 3
* E37LR dome/reading lamps - left rear terminal 3
* E37RF dome/reading lamps - right front terminal 3
* E37RR dome/reading lamps - right rear terminal 3
* S48C multifunction switch 1 - instrument panel terminal 1
* S48D multifunction switch 2 - instrument panel terminal 1
* S32LR seat heating switch - left rear terminal 1
* S32LR seat heating switch - right rear terminal 1
* S79LR window switch - left rear terminal 6
* S79RR window switch - right rear terminal 6
4. Verify the test lamp turns ON and OFF when commanding the LED Backlight Dimming ON and OFF with a scan tool.
• If the test lamp is always OFF
1. Ignition OFF, disconnect the appropriate harness connector at the K9 body control module.
2. Test for infinite resistance between the control circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance
3. Test for less than 2 ohms in the control circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the K9 body control module.
• If the test lamp is always ON
1. Ignition OFF, disconnect the appropriate harness connector at the K9 body control module, ignition ON.
2. Test for less than 1 V between the control circuit terminal and ground.
• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V, replace the K9 body control module.
• If the test lamp turns ON and OFF
5. Test or replace the component with inoperative backlighting.
Switch Indicator LED Backlighting Malfunction
Note: Each component with backlighting may need to be disconnected to isolate a short to voltage or short to ground. Use the schematics to identify the following:
* Backlighting components the vehicle is equipped with
* Each component's control and ground circuit terminals
* Component locations on the backlighting control circuit
1. Ignition OFF, scan tool disconnected, all doors closed, all accessories OFF, disconnect the harness connector at the component with inoperative indicator LED backlighting. It may take up to 2 minutes for all vehicle systems to power down.
2. Test for less than 15 ohms between the appropriate ground circuit terminal listed below and ground.
* S48C multifunction switch 1 - instrument panel terminal 5
* S48D multifunction switch 2 - instrument panel terminal 5
* S32LR seat heating switch - left rear terminal 3
* S32RR seat heating switch - right rear terminal 3
• If 5 ohms or greater
1. Ignition OFF.
2. Test for less than 2 ohms in the ground circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, repair the open/high resistance in the ground connection.
• If less than 5 ohms
3. Connect a test lamp between the appropriate control circuit terminal listed below and ground.
* S48C multifunction switch 1 - instrument panel terminal 3
* S48D multifunction switch 2 - instrument panel terminal 3
* S32LR seat heating switch - left rear terminal 6
* S32RR seat heating switch - right rear terminal 6
4. Verify the test lamp turns ON and OFF when commanding the LED Backlight Dimming ON and OFF with a scan tool.
• If the test lamp is always OFF
1. Ignition OFF, disconnect the X1 harness connector at the K9 body control module.
2. Test for infinite resistance between the control circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance
3. Test for less than 2 ohms in the control circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the K9 body control module.
• If the test lamp is always ON
1. Ignition OFF, disconnect the X1 harness connector at the K9 body control module, ignition ON.
2. Test for less than 1 V between the control circuit terminal and ground.
• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V, replace the K9 body control module.
• If the test lamp turns ON and OFF
5. Test or replace the component with inoperative switch indicator LED backlighting.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the repair.
* Rear Seat Heater Switch Replacement Rear Seat Heater Switch Replacement
* Center Reading and Courtesy Lamp Replacement Center Reading and Courtesy Lamp Replacement
* Interior Lamp Switch Replacement (Override) Interior Lamp Switch Replacement (Override)Interior Lamp Switch Replacement (Reading) Interior Lamp Switch Replacement (Reading)
* Control Module References Control Module References for BCM replacement, programming, and setup