The instrument panel (I/P) dimmer switch is used to increase and decrease the brightness of the interior backlighting components. The body control module (BCM) supplies a 12-volt reference through the instrument panel (I/P) dimming voltage reference circuit to the interior lamp dimmer switch, which is part of the headlamp switch. When the dimmer switch is placed in a desired brightness position, reference voltage is applied through the dimmer switch rheostat and the I/P lamps dimmer switch signal circuit to the BCM. The BCM interprets this voltage signal, then applies a pulse width modulated (PWM) voltage through the I/P lamps control circuit and the LED dimming control circuit to all related interior lamps, illuminating them to the desired level of brightness.

The ignition is ON.

The I/P lamps are not illuminated.

A history DTC will clear once 100 consecutive malfunction-free ignition cycles have occurred.

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

Ignition ON, cover the ambient light sensor, vary the interior lamp dimming switch from dim to full bright. The I/P lamps should dim and then become full bright.

1. Ignition OFF, disconnect the harness connector at the headlamp switch.
2. Ignition ON, test for 11.8-12.2 volts between the 12-volt reference circuit terminal 15 and ground.

⇒	If greater than the specified range, test the 12-volt reference circuit for short to voltage. If the circuit tests normal, replace the BCM.

⇒	If less than the specified range, test the 12-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.

3. Verify the scan tool Dimming Control Signal parameter is less than 0.75 volts.

⇒	If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the BCM.

4. Install a 3A fused jumper wire between the signal circuit terminal 13 and the 12-volt reference circuit terminal 15. Verify the scan tool Dimming Control Signal parameter is greater than 11.294 volts.

⇒	If less than the specified value, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.

5. If all circuits test normal, test or replace the headlamp switch.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.