The left and right front door courtesy lamps are controlled, and receive voltage and ground from the drivers door module (DDM) and the passenger door module (PDM) respectively. The body control module (BCM), DDM, and the PDM communicate through class II serial data for the lamp illumination commands and the door ajar switches.
The remaining courtesy lamps are controlled and receive voltage from the BCM. Voltage for the courtesy lamp supply voltage circuit and the backup lamp supply voltage circuit is from the TBC B fuse in the instrument panel fuse block directly through the BCM to these circuits. A short to ground on either of these circuits will open the fuse. Ground is provided to the footwell lamps and all courtesy/reading lamps at G203. Ground is provided to the right middle and right rear door at G306. Ground is provided to the left middle and left rear door at G302.
There could be a DTC - diagnostic trouble code stored in the BCM
The body control module (BCM) receives a ground signal from the door jamb, liftglass/liftgate if equipped, or courtesy lamp switches requesting courtesy/dome lamp illumination. When this occurs, the BCM directly sends a voltage through the courtesy lamp supply voltage circuit illuminating the courtesy/dome lamps.
Voltage for the courtesy lamp supply voltage circuit as well as the backup lamp supply voltage circuit is from the left instrument panel fuse block TBC 2B 15-amp fuse directly through the BCM to these circuits
The body control module (BCM) monitors the courtesy lamp switch signal circuit in order to determine when the courtesy/dome lamps should be illuminated. When the BCM senses that the courtesy lamp switch signal circuit is grounded when the switch is activated, the BCM will illuminate the courtesy/dome lamps.
Inspect the following related body control module (BCM), driver door module (DDM), and passenger door module (PDM) data parameters. Refer to Scan Tool Data List
or Scan Tool Data Definitions
for typical values and definitions:
The courtesy lamp switch
The interior lamp defeat switch
The door ajar switches
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