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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Headlamp Switch B+
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B1405 03, B1529 03, B257B 03, 1
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B257B 03, 1
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-
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-
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Instrument Panel Lamps Dimmer Switch Signal
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B257B 03, 1
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B257B 03, 1
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B257B 07
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-
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Interior Backlighting Control BCM Terminal 9 X7
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B2625 02
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2
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1
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-
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Interior Backlighting Control BCM Terminal 8 X2
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B2625 02, 2
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2
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1
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-
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Interior Backlighting Control BCM Terminal 5 X1 (with UD5)
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B2625 02
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2
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1
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-
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Headlamp Switch Ground
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-
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B257B 03
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-
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-
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1. Interior backlighting at full intensity and cannot be dimmed
2. Interior backlighting component does not illuminate
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Circuit/System Description
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The dimmer switch is used to increase and decrease the brightness of the interior backlighting components. The body control module (BCM) supplies a reference voltage to the backlight dimmer switch, which is part of the headlamp switch. When the dimmer switch is placed in a desired brightness position, the dimmed voltage setting is applied through the dimmer switch and the dimmer switch signal circuit to the BCM. The BCM interprets this voltage signal, then applies a pulse width modulated (PWM) voltage through the backlight lamp control circuit and the LED dimming control circuit illuminating the components to the requested level.
Schematic Reference
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 scan tool information
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Circuit/System Verification
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1.
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Ignition ON, observe the scan tool Indicator Dimming Duty cycle Command parameter while operating the dimmer switch from high to low. The parameter should change 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 the Dimmer Switch Circuit Test.
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3.
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Observe the interior backlighting components while commanding the LED Backlight Dimming ON and OFF with the scan tool. The backlighting should turn ON and OFF when changing between the commanded states.
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4.
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If the backlighting does not change between the commanded states, refer to the 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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Test for less that 10 Ω between the ground circuit terminal 6 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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Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 1 and ground.
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5.
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If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K9 BCM.
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6.
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Ignition ON, test for less than 0.3 V between signal circuit terminal 12 and ground.
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7.
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If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the K9 BCM.
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8.
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Install a 3 A fused jumper wire between the signal circuit terminal 12 and the B+ circuit terminal 1. The interior backlighting should be dimmed.
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9.
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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 BCM.
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10.
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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, disconnect the harness connector at the appropriate backlighting component.
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2.
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Test for less than 5.0 Ω between the ground circuit terminal 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 and ground.
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5.
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Ignition ON, command the LED Backlight Dimming 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 BCM.
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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 BCM.
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8.
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If all circuits test normal, test or replace the component with the inoperative backlighting.
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Perform the
Diagnostic Repair Verification
after completing the diagnostic procedure.
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•
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Refer to the appropriate replacement procedure for the lighting component that requires replacement.
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