Interior Backlighting Malfunction
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Interior Backlighting Malfunction
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Diagnostic Fault Information
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Circuit
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Short to Ground
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Open/High Resistance
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Short to Voltage
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Signal Performance
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Dimming 12V Reference
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B257B 03, B1405 03, B1529 03
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B257B 03
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-
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-
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Instrument Panel Lamps Dimmer Switch Signal
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B257B 03
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B257B 03
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B257B 07
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Interior Backlighting Control
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B2610 02
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2
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1
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Interior Backlighting Ground
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-
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2
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-
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1. Interior backlighting at full Intensity and cannot be dimmed
2. Interior backlighting does not illuminate
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Circuit/System Description
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The body control module (BCM) supplies a reference voltage to the backlight dimmer switch, which is part of the headlamp switch. When the backlight dimmer switch is placed in a desired brightness position, reference voltage is applied through the backlight dimmer switch resistor ladder to the BCM. The BCM interprets this voltage signal, then applies a pulse width modulated (PWM) voltage to the LED dimming supply circuit to all related interior lamps, illuminating them to the desired level of brightness.
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Heated Seat Control Module Driver
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Rear Window Sunshade Switch
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Intrusion Sensor Defeat Switch
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Outside Rearview Mirror Switch
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Park Brake Control Switch
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Automatic Transmission Shift Lever
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Multi Function Switch - Instrument Panel
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Steering Wheel Controls Switches
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Universal Garage Door Opener
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Schematic Reference
Interior Lights Schematics
Interior Lights Dimming Schematics
Connector End View Reference
Component Connector End Views
Description and Operation
Interior Lighting Systems Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References
for information on diagnostic tools
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Circuit/System Verification
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1.
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Ignition ON, observe the scan tool Indicator Backlight Command parameter while operating the dimmer switch from high to low. The parameter should indicate between 5-50% when the backlight switch is moved up and down.
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2.
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If the reading does not change, refer to Dimmer Switch Circuit Test.
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3.
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Command the LED Backlight Dimming test with the scan tool. The appropriate incandescent lighting items should go ON and OFF.
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4.
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If the backlighting does not go ON and OFF, refer to Interior Backlighting Circuit Test.
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Dimmer Switch Circuit Test
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1.
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Ignition OFF, disconnect the harness connector at the S30 Headlamp Switch.
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2.
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Ignition ON, test for greater than 11 V between the 12 V reference circuit terminal 1 and ground.
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3.
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If greater than the specified range, test the 12 V reference circuit for a short to voltage. If the circuit tests normal, replace the K9 Body Control Module.
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4.
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If less than the specified range, test the 12 V reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K9 Body Control Module.
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5.
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Ignition ON, test for less than 0.3 V between dimming signal circuit terminal 12 and ground.
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6.
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If greater than the specified range, test the dimming signal circuit terminal 12 for a short to voltage. If the circuit tests normal, replace the K9 Body Control Module.
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7.
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Install a 3 A fused jumper wire between the signal circuit terminal 12 and the 12 V reference circuit terminal 1. The interior backlighting should now be dimmed.
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8.
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If the interior backlighting is not dimmed, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K9 Body Control Module.
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9.
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If all circuits test normal, test or replace the S30 Headlamp Switch.
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Interior Backlighting Circuit Test
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1.
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Ignition OFF, interior light switched OFF, disconnect the harness connector at the appropriate inoperative backlighting component.
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2.
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Test for less than 5.0 Ω between the ground circuit terminal black wire and ground.
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3.
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If greater than the specified range, test the ground circuit for an open/high resistance.
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4.
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Connect a test lamp between the control circuit terminal yellow wire and ground.
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5.
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Ignition ON, command the LED Backlight Dimming test ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
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6.
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If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K9 Body Control Module.
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7.
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If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the K9 Body Control Module.
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8.
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If all circuits test normal, test or replace the appropriate component with the inoperative backlighting.
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Perform the
Diagnostic Repair Verification
after completing the diagnostic procedure.
