B1398

DTC B1398

Circuit Description

The body control module (BCM) controls the dimming operation of the interior lamps. The BCM applies a 12-volt reference signal to the instrument panel (I/P) dimming switch. When you move the I/P dimming switch, the BCM uses this varying voltage signal in order to apply a pulse width modulation (PWM) voltage in order to control the brightness of the interior illumination lamps.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B1398 Dimming Reference Voltage Circuit High

Conditions for Running the DTC

* Voltage supplied to the module is in the normal operating range, approximately 10-16 volts.
* The interior lamps must be ON.

Conditions for Setting the DTC

* The BCM detects a short to battery positive voltage in the dimming reference voltage circuit.
* The condition is present for longer than 3 ms.

Action Taken When the DTC Sets

The BCM stores DTC B1398 in memory.

Conditions for Clearing the MIL/DTC

* A current DTC B1398 clears when the BCM no longer detects a short to battery positive voltage in the dimming reference voltage circuit.
* A history DTC B1398 clears after 100 consecutive ignition cycles.

Diagnostic Aids

* If the DTC B1398 is a history DTC, the fault may be intermittent. Refer to Testing for Intermittent Conditions and Poor Connections. Component Tests and General Diagnostics
* An intermittent short to battery positive voltage in the following locations may cause an intermittent malfunction to occur:

- The dimming reference voltage circuit
- The I/P dimming switch
- The BCM

Test Description

Step 1 - Step 7:

The numbers below refer to the step numbers on the diagnostic table.
2. This step tests the dimming reference circuit for a short to battery positive voltage.
3. This step tests the dimming return circuit for a short to battery positive voltage.