Component Functional Description And Technical Data

Base Vehicles:  The Body Control Module (BCM) receives hardwired inputs from the Driver and Passenger Door Lock Switches through the Left or Passenger Door Lock Switch Status circuits.

Premium Vehicles:  The BCM receives Door Lock and Unlock CAN Bus messages from the Driver Door Module (DDM) and Passenger Door Module (PDM).

All Vehicles:  The BCM receives Door Lock and Unlock CAN Bus messages from the Radio Frequency (RF-Hub) Module, based on inputs from the Finger Operated Button with Integrated Key (FOBIK).

FUNCTIONAL OPERATION OF LOCK MOTORS:  Based on the Door Lock and Unlock requests received, the BCM controls the Lock and Unlock functions of the bidirectional Driver, Passenger, and Rear Door Lock/Unlock Motors, which are integral to the Door Latches. The BCM controls three internal relays (Door Lock, Driver Door Unlock, Passenger Door Unlock) to operate the Door Lock/Unlock Motors. When the BCM internal relays are inactive, a ground path is provided through the Driver Door Lock Switch Return circuit to the Driver and Passenger Door Lock/Unlock Switches and Motors. For the Left and Right Rear Doors, a separate ground is provided to the Door Lock/Unlock Motors through the wiring harness to the body sheet-metal.

When the Door Lock/Unlock Motors are activated, the BCM will operate the motors for approximately 370 milliseconds. The Door Lock/Unlock Motors operate in the voltage range of 9.0 and 16.0 volts. Typical current draw for the Door Lock/Unlock Motors are listed in amperes in the table below.

Driver Door Lock:  When the BCM receives a Door LOCK request, the BCM activates the Door Lock Relay, which provides a voltage signal on the Door Lock Relay Output circuit and actuates the Driver Door Lock/Unlock Motor to the LOCK position. A ground path is provided to the Lock/Unlock Motor from the inactive Driver Door Unlock Relay, through the Driver Door Unlock Driver circuit.

Driver Door Unlock:  When the BCM receives a Door UNLOCK request, the BCM activates the Driver Door Unlock Relay, which provides a voltage signal on the Driver Door Unlock Driver circuit, which and actuates the Driver Door Lock/Unlock Motor to the UNLOCK position. A ground path is provided to the Lock/Unlock Motor from the inactive Door Lock Relay, through the Door Lock Relay Output circuit.

Passenger and Rear Doors Lock:  When the BCM receives a Door LOCK request, the BCM activates the Door Lock Relay, which provides a voltage signal on the Door Lock Relay Output circuit and actuates the Passenger and Rear Door Lock/Unlock Motors to the LOCK position. A ground path is provided to the Lock/Unlock Motors from the inactive Passenger Door Unlock Relay, through the Passenger Door Unlock Driver circuit.

Passenger and Rear Doors Unlock:  When the BCM receives a Door UNLOCK request, the BCM activates the Passenger Door Unlock Relay, which provides a voltage signal on the Passenger Door Unlock Driver circuit and actuates the Passenger and Rear Door Lock/Unlock Motors to the UNLOCK position. A ground path is provided to the Lock/Unlock Motors from the inactive Door Lock Relay, through the Door Lock Relay Output circuit.

FUNCTIONAL OPERATION OF DOOR AJAR SWITCHES:  The Door Ajar Switches are integral to the Door Latches and are monitored by the BCM to determine if they are closed or ajar. The Door Ajar Switches are wake-up signals to the BCM. The BCM broadcasts the Driver Door Ajar Switch status over the CAN bus for other modules that require the Driver Door Latch state.

The Driver Door Ajar Switch status must be rationalized for certain vehicle features to function. Unlike the Passenger and Rear Door Ajar Switches, which functions like traditional open/closed Door Ajar Switches, the Driver Door Latch uses redundant Primary and Secondary Door Ajar Switches for diagnostic purposes. The Primary and Secondary Door Ajar Switches share a common return circuit.

• Primary and Secondary Driver Door Ajar Switches:  The BCM uses an internal pull up 1000 Ohm resistor for the Primary and Secondary Door Ajar Switch Signal circuits. Both Door Ajar Switches are each equipped with internal 604 Ohm and 1070 Ohm resistors. When the Primary or Secondary Door Ajar Switch is open, the resistance through the switch is 1674 Ohms. When the Door Ajar Switch is closed, the resistance through the switch is 604 Ohms. The Primary and Secondary Door Ajar Switch states oppose each other, meaning that when the Driver Door/Latch is closed, the Primary Door Ajar Switch is in the open state, but the Secondary Door Ajar Switch is in the closed state. When the Driver Door/Latch is opened, the Primary Door Ajar Switch is in the closed state, but the Secondary Door Ajar Switch is in the open state.
• Passenger and Rear Door Ajar Switches:  When a Passenger or Rear Door is closed (Door Latch is closed), the Door Ajar Switch is in the open state. When a Passenger or Rear Door is opened (Door Latch is opened), the Door Ajar Switch is in the closed state and the circuit is connected to ground. Therefore, the Passenger and Rear Door Ajar Switch Signal inputs to the BCM are high when the Door is closed, and low when the Door is opened.

  NOTE:  On vehicles equipped with both a Manual Transmission and Engine Stop/Start (ESS), the Passenger Door Ajar Switch will operate similar to the Primary Driver Door Ajar Switch.

DIAGNOSTIC OVERVIEW: 

• Door Lock/Unlock Motors:  The BCM is capable of detecting open and short circuits in the H-Bridge Door Lock/Unlock Control circuits. The Door Lock/Unlock Motors are not thermally protected by the BCM. Thermal protection is accomplished by limiting the number of actuations within a calibrated period of time.
• Door Ajar Switches:  The resistors in the Primary and Secondary Driver Door Ajar Switches allows the BCM to perform diagnostics on the circuits and switches. Unlike the Passenger and Rear Door Ajar Switches, the voltage on the Primary and Secondary Driver Door Ajar Switch Signal circuits should not be high or low. If the BCM observes the voltage on either of the Signal circuits is high, low or out of range, a DTC will set.