Interior Backlighting Malfunction

Diagnostic Instructions Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Review Strategy Based Diagnosis for an overview of the diagnostic approach. Diagnostic Procedure Instructions provides an overview of each diagnostic category. Diagnostic Fault Information

Circuit	Circuit Function	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performan
7555	Signal	B1918 16	1	B1918 17	1
7556	Low Reference	—	1	—	—
6817	Control	B1837 11	1	B1837 12	—
*	Ground	—	1	—	—
1. Dimmer Switch Malfunction 2. Interior Dimming Malfunction *. Refer to the schematic to identify the appropriate ground circuits

Scan Tool Functions K9 Body Control Module – Data Display – Interior Lighting Data

Data Parameter	Description
Dimmer Switch	This data parameter will increase/decrease percentage as the dimmer switch +/- buttons are pressed

Circuit/System Description The S30 Headlamp Switch is used to control the interior backlight dimming. The K9 Body Control Module (BCM) provides 5 V signal circuit 7555 and low reference circuit 7556 to the headlamp switch for backlight dimming and fog light controls. When a dimming/fog light button is pressed, the signal circuit becomes grounded through the appropriate resistor internal to the headlight switch and voltage from the BCM will decrease accordingly. The BCM interprets the signal and responds by applying the correct amount of pulse width modulated (PWM) voltage to circuit 6817 resulting in the desired amount of backlighting intensity. Reference Information Schematic Reference Interior Lights Dimming Schematics Connector End View Reference Master Electrical Component List Description and Operation Interior Lighting Systems Description and Operation Electrical Information Reference Circuit Testing Connector Repairs Testing for Intermittent Conditions and Poor Connections Wiring Repairs Scan Tool Reference Control Module References for scan tool information Circuit/System Verification

1. Ignition on/vehicle in service mode.
2. Verify the Dimmer Switch data parameter increases/decrease percentage when adjusting the interior dimming level up/down with the dimmer switch. ⇒ If the parameter does not change Refer to Circuit/System Testing – Dimmer Switch Malfunction. ⇓ If the parameter changes

Note

Use the schematics to identify the interior backlighting components the vehicle is equipped with on circuit 6817.

3. Verify all backlight dimming components change lighting intensity while adjusting the dimmer switch. ⇒ If one or more backlight dimming components do not change lighting intensity Refer to Circuit/System Testing – Interior Backlighting Malfunction. ⇓ If all of the backlight dimming components change lighting intensity
4. A fault is not currently present and may be an intermittent condition. Circuit/System Testing Dimmer Switch Malfunction
5. Ignition off, disconnect the connector at the S30 Headlamp Switch, ignition on.
6. Verify a test lamp illuminates between low reference terminal 12 and B+. ⇒ If the test lamp does not illuminate 2.1. Test circuit 7556 for an open/high resistance. ⇒ If an open/high resistance is found, repair the fault on the circuit. ⇓ If an open/high resistance is not found. 2.2. Replace the K9 Body Control Module. ⇓ If the test lamp illuminates
7. Test for 4.8 V – 5.2 V between signal circuit terminal 11 and ground. ⇒ If less than 4.8 V 3.1. Test circuit 7555 for a short to ground. ⇒ If a short to ground is found, repair the fault on the circuit. ⇓ If a short to ground is not found 3.2. Test circuit 7555 for an open/high resistance. ⇒ If an open/high resistance is found, repair the fault on the circuit. ⇓ If an open/high resistance is not found. 3.3. Replace the K9 Body Control Module. ⇒ If greater than 5.2 V 3.1. Test circuit 7555 for a short to voltage. ⇒ If a short to voltage is found, repair the fault on the circuit. ⇓ If a short to voltage is not found. 3.2. Replace the K9 Body Control Module. ⇓ If 4.8 V – 5.2 V
8. Replace the S30 Headlamp Switch.

Note

Circuit/System Verification must be performed before Circuit/System Testing. 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, disconnect the connector at the component with inoperative backlighting.
2. Verify a test lamp illuminates between the appropriate ground circuit terminal and B+. ⇒ If the test lamp does not illuminate 2.1. Repair the open/high resistance on the ground circuit or ground connection. ⇓ If the test lamp illuminates
3. Ignition on/vehicle in service mode, connect a test lamp between the appropriate control circuit terminal and ground.
4. Verify the test lamp illuminates and changes intensity when adjusting the dimmer switch. ⇒ If the test lamp does not illuminate 4.1. Test circuit 6817 for a short to ground. ⇒ If a short to ground is found, repair the fault on the circuit. ⇓ If a short to ground is not found. 4.2. Test circuit 6817 for an open/high resistance. ⇒ If an open/high resistance is found, repair the fault on the circuit. ⇓ If an open/high resistance is not found. 4.3. Replace the K9 Body Control Module. ⇒ If the test lamp illuminates but does not change intensity 4.1. Test circuit 6817 for a short to voltage. ⇒ If a short to voltage is found, repair the fault on the circuit. ⇓ If a short to voltage is not found. 4.2. Replace the K9 Body Control Module. ⇓ If the test lamp illuminate and changes intensity
5. Test or replace the component with inoperative backlighting. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair. Lighting Component Replacement Reference Control Module References for BCM replacement, programming, and setup