B2457

DTC B2457 Theater Dimming 2 Circuit Shorted To Ground/Open:

DTC B2457 Theater Dimming 2 Circuit Shorted To Ground/Open (Part 1 Of 2):

DTC B2457 Theater Dimming 2 Circuit Shorted To Ground/Open (Part 2 Of 2):

CIRCUIT DESCRIPTION
The Body Control Module (BCM) controls interior illumination. The BCM turns on the roof rail courtesy/reading lamps and the dome lamp when:
^ Any vehicle door is opened.
^ The IP dimmer switch is in the DOME position.
^ During exit illumination or delayed illumination.
^ When unlocking the doors using the keyless entry transmitter.

The BCM turns off these lamps when all doors are closed and the IP dimmer switch is off.

All vehicle doors contain a door lock ajar switch. When the driver's door is open, the LF door lock ajar switch closes and sends a ground signal to the BCM through circuit 49. When one of the LF, RF, LR or RR door is open, its corresponding door lock ajar switch closes and sends a ground signal to the BCM through circuit 727. The BCM grounds circuit 157 when detecting a ground signal in either circuit 49 or 727.

When the driver's door is closed, the LF door lock ajar switch opens circuit 49. When the LF, RF, LR and RR doors are closed, their corresponding door lock ajar switches open circuit 727. The BCM then opens circuit 157 when either circuit 49 or 727 is open.

The BCM uses the voltage in circuit 240 to power the courtesy lights through circuit 1732. The BCM controls the power supplied in circuit 1732 for inadvertent load (battery rundown) protection. The BCM opens circuit 157 when the inadvertent load (battery rundown) protection is active (circuit 1732 is open.)

CONDITIONS FOR SETTING THE DTC
^ The BCM detects a short to ground or an open in circuit 157 for more than 0.15 seconds.
^ The BCM detects an open in circuit 1732.

ACTION TAKEN WHEN THE DTC SETS
The BCM stores DTC B2457 in memory.

CONDITIONS FOR CLEARING THE DTC
^ The BCM no longer detects a short to ground in circuit 157.
^ The BCM no longer detects an open in circuit 157 or 1732
^ A history DTC will clear after 100 consecutive ignition cycles if the condition for the fault is no longer present.
^ Using a scan tool.

DIAGNOSTIC AIDS
^ The following conditions may cause an intermittent malfunction to occur:
- An intermittent short to ground in circuit 157.
- An intermittent open in circuit 157 or 1732.
- The BCM is shorted to ground or open internally.
^ If the DTC is a history DTC, the problem may be intermittent. Try performing the tests shown while wiggling wiring and connectors, this can often cause the malfunction to reappear.
^ DTC P 1626 will set in the Powertrain Control Module (PCM) when the ignition switch is in the RUN position with the BCM disconnected. When BCM diagnostics and repairs are completed, refer to the Engine Controls for additional information on PCM related DTCs. Powertrain Management

TEST DESCRIPTION
Numbers below refer to the step numbers on tile diagnostic table.
3. Checks for a short to ground in circuit 157.
4. Checks for an open in circuit 157.
5. Determines whether the malfunction is intermittent or the BCM is faulty.