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.
- 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

Steps 1 - 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.