The body control module (BCM) supplies a voltage 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 LED dimming supply circuit illuminating the heated seat switches to the requested level.

The ignition is ON.

The BCM detects a short to ground on the LED dimming supply circuit.

The BCM will not attempt to illuminate the LED indicator lamps.

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 LED lamps should dim and then become full bright.

1. Ignition OFF, disconnect the harness connectors at all components fed by the LED backlight dimming supply circuit terminal 25 X3.
2. Ignition ON, clear the DTC with a scan tool.
3. Operate the vehicle within the conditions for running the DTC and verify the DTC does not reset.

⇒	If the DTC resets, test the LED dimming supply circuit for a short to ground. If the circuit test normal, replace the BCM.

4. Reconnect each component one at a time and verify that the DTC does not reset as current.

⇒	If the DTC resets as current, test or replace the component responsible for setting the DTC.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.