Orlando

DTC B257B

The body control module (BCM) supplies a reference voltage to the 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 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.

The ignition is ON.

B257B 03

The BCM detects a voltage that is lower than 0.3 V on the dimming voltage circuit.

B257B 07

The BCM detects a voltage that is greater than 12.2 V on dimming voltage circuit.

The BCM will not dim or illuminate any LED backlighting supplied by the backlight lamp control circuits.

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, turn the parking lamps ON, vary the interior backlight from dim to full bright by using the dimmer switch. The interior backlighting should dim and then become full bright.

1. Ignition OFF, disconnect the X1 and X3 harness connectors at the K9 Body Control Module.
2. Ignition ON, test for less than 0.3 V between the signal circuit terminal 9 X1 and ground.

⇒	If greater than the specified value, test the circuits listed below for a short to voltage. If the circuit tests normal, replace the S30 Headlamp Switch.

•	Signal circuit terminal 9 X1

•	12 V reference voltage circuit terminal 4 X3

3. Ignition OFF, test for infinite resistance between the signal circuit terminal 9 X1 and ground.

⇒	If less than infinite resistance, test the circuits listed below for a short to ground. If the circuit tests normal, replace the S30 Headlamp Switch.

•	Signal circuit terminal 9 X1

•	12 V reference voltage circuit terminal 4 X3

4. Test for 7.4-7.9 kΩ between the signal circuit terminal 9 X1 and the 12 V reference voltage circuit terminal 4 X3.

⇒	If less than 7.4 kΩ, test the signal circuit and the 12 V reference circuit for a short circuit. If the circuit tests normal, replace the S30 Headlamp Switch.

⇒	If greater than 7.9 kΩ, test the signal circuit and the 12 V reference circuit for an open/high resistance. If the circuit tests normal, replace the S30 Headlamp Switch.

5. Test for 3.7-4.1 kΩ between the signal circuit terminal 9 X1 and the 12 V reference voltage circuit terminal 4 X3 while turning the thumbwheel for dimming up.

⇒	If not the specified range, replace the S30 Headlamp Switch.

6. Test for 5.1-5.5 kΩ between the signal circuit terminal 9 X1 and the 12 V reference voltage circuit terminal 4 X3 while turning the thumbwheel for dimming down.

⇒	If not the specified range, replace the S30 Headlamp Switch.

7. Test for 2.7-3.1 kΩ between the signal circuit terminal 9 X1 and the 12 V reference voltage circuit terminal 4 X3 while pressing the front fog lamp switch.

⇒	If not the specified range, replace the S30 Headlamp Switch.

8. Test for 2.0-2.4 kΩ between the signal circuit terminal 9 X1 and the 12 V reference voltage circuit terminal 4 X3 while pressing the rear fog lamp switch.

⇒	If not the specified range, replace the S30 Headlamp Switch.

9. If all circuits test normal, replace the K9 Body Control Module.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.