B1398

CIRCUIT DESCRIPTION
The BCM controls the dimming operation of the interior lamps. The BCM applies a 12-volt reference signal to the IP dimming switch. When you move the IP 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

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 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 and Poor Connections in Diagnostic Aids.
^ An intermittent short to battery positive voltage in the following locations may cause an intermittent malfunction to occur:
- The dimming reference voltage circuit
- The IP dimming switch
- The body control module (BCM)

TEST DESCRIPTION

Steps 1-7:

The number(s) below refer to the step number(s) 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.