GM Service Manual Online
For 1990-2009 cars only

Circuit Operation

The body control module (BCM) is designed with an internal antenna. The BCM picks up transmitted radio frequencies from a hand held remote control door lock transmitter. The transmitter has sufficient power for operating the system from up to 7-10 meters (22-33 ft) from the vehicle.

The side door lock actuators and the rear compartment lid release actuator contain an electronic circuit breaker (ECB). ECB resistance increases if the actuator is overloaded. Resistance returns to normal after the voltage is removed from the actuator terminals.

Remote Control Door Lock Transmitter Functions

Lock

When the lock button on the remote control door lock transmitter is pressed, the body control module (BCM) grounds the coil of relay 5. A voltage pulse is applied from the BCM through circuit  295 to both side door lock actuators. Ground is applied from G200 through circuit  650, the BCM and circuit 694 and circuit 1663 to the actuators. the driver and passenger doors lock. The BCM turns off all of the courtesy lamps as a visual confirmation that a lock function was performed.

Unlock

When the unlock button on the remote control door lock transmitter is pressed once, the body control module  (BCM) grounds the coil of relay 3. A voltage pulse is applied from the BCM through circuit  694 to the left side door lock actuator. Ground is applied from G200 through circuit 650, the BCM and circuit  295 to the actuator. The driver door unlocks. The BCM also grounds the dome/courtesy lamps through CKT 156 for approximately 40 seconds to provide illuminated entry. The BCM then initiates the theater dimming function until the BCM receives an ignition ON input.

When the unlock button on the transmitter is pressed a second time within 5 seconds, the BCM grounds the coil of relay 3. A voltage pulse is applied from the BCM through circuit  1663 to the right side door lock actuator. Ground is applied from G200 through circuit 650, the BCM and circuit  295 to the actuator. The passenger door unlocks.

Rear Compartment Lid Release

Automatic Transmission

Voltage is applied at all times from the PWR ACCY fuse through circuit  640 to the normally open contacts of the rear compartment lid release relay. When the rear compartment lid release button on the remote control door lock transmitter is pressed twice , voltage is applied from the body control module (BCM) through circuit  253 to the coil of the rear compartment lid release relay. If the transmission is in the PARK or NEUTRAL position, the relay is energized. The relay then applies battery voltage through circuit 56 to the rear compartment lid release actuator. Ground is applied from G400 through circuit  1550 to the actuator. The rear compartment lid opens.

Manual Transmission

Voltage is applied at all times from the PWR ACCY fuse through circuit  640 to the normally open contacts of the rear compartment lid release relay. When the rear compartment lid release button on the remote control door lock transmitter is pressed twice , voltage is applied from the body control module (BCM) through circuit  253 to the coil of the rear compartment lid release relay. If the park brake is set, the park brake switch is closed and the relay is energized. The relay then applies battery voltage through circuit 56 to the rear compartment lid release actuator. Ground is applied from G400 through circuit  1550 to the actuator. The rear compartment lid opens.

Illuminated Entry Operation

The dome lamp (coupe) or the rear courtesy lamps illuminate whenever a remote control door lock transmitter unlock request is received by the body control module (BCM). The BCM provides voltage through circuit  149 to the dome lamp (coupe) or the rear courtesy lamps (convertible). Ground is applied from the BCM through circuit  156 to the lamps. The lamps illuminate whenever a remote control door lock transmitter request is received.

With a LOCK request, the dome lamp (coupe) or the rear courtesy lamps (convertible) are immediately turned off. This action provides visual confirmation that a lock function was performed.

With an unlock or a rear compartment lid release request, the dome lamp (coupe) or the rear courtesy lamps (convertible) are turned on. The lights remain on for 40 seconds in order to provide illuminated entry and hatch area illumination.

Illuminated entry is disabled when the BCM detects ignition ON voltage.

Programming the Body Control Module

The body control module (BCM) is capable of being programmed for up to four keyless entry transmitters. When four transmitters are programmed, they must be programmed one after the other during the same program sequence. Transmitters may not be programmed simultaneously. The BCM can only be programmed by the transmitters while in the program mode.