Without Intelligent Access (IA)

Handles, Locks, Latches and Entry Systems - Without Intelligent Access (IA)

Principles of Operation

Power Locks

The Body Control Module (BCM) monitors the door lock control switches. When the BCM (Body Control Module) receives an unlock/lock command from either door lock control switch, the BCM (Body Control Module) energizes a relay (internal to the BCM (Body Control Module)) to supply the correct power and grounds for the door lock actuators.

Liftgate Release

The liftgate release switch operates the liftgate latch electronically. When the switch is pressed, the BCM (Body Control Module) processes the input and releases the liftgate latch.

The doors must be unlocked electronically in order for the BCM (Body Control Module) to release the liftgate latch. When this condition is met and the BCM (Body Control Module) receives the input from the liftgate release switch, the BCM (Body Control Module) provides power to the latch release motor. For the power liftgate, refer to Doors, Hood and Trunk.

Remote Keyless Entry (RKE)

The Remote Keyless Entry (RKE) feature is controlled by BCM (Body Control Module). The BCM (Body Control Module) receives the RKE (Remote Keyless Entry) inputs from the Tire Pressure Monitor (TPM) module over the Medium Speed Controller Area Network (MS-CAN). When any RKE (Remote Keyless Entry) transmitter button is pressed, the signal is received by the TPM (Tire Pressure Monitor) module internal antenna. The TPM (Tire Pressure Monitor) module then filters the RKE (Remote Keyless Entry) signal received to make sure it is a programmed transmitter. If the signal received is from a programmed transmitter, the TPM (Tire Pressure Monitor) module sends the RKE (Remote Keyless Entry) command to the BCM (Body Control Module) over the MS-CAN (Medium Speed Controller Area Network). The BCM (Body Control Module) then interprets the RKE (Remote Keyless Entry) command and activates the corresponding output.

The BCM (Body Control Module) requests the illuminated entry feature to turn the interior lamps on when an unlock command is received. If a lock command is received, the illuminated entry feature turns off. The BCM (Body Control Module) then supplies voltage to the appropriate door lock actuator(s) to lock or unlock the doors. The RKE (Remote Keyless Entry) transmitter can also be used to activate the panic alarm. On vehicles with memory, the RKE (Remote Keyless Entry) transmitter also causes the BCM (Body Control Module) to send a MS-CAN (Medium Speed Controller Area Network) message to the Driver Seat Module (DSM) to activate all memory features to the positions associated with the RKE (Remote Keyless Entry) transmitter being used.

If equipped with a power liftgate, the BCM (Body Control Module) sends a request to the Liftgate/Trunk Module (LTM) to open or close the power liftgate.

Remote Start

The factory equipped remote start system is controlled by the BCM (Body Control Module). How the BCM (Body Control Module) receives the remote start command from an Integrated Keyhead Transmitter (IKT) is very similar to the RKE (Remote Keyless Entry) function. For additional information on the factory equipped remote start system, refer to Starting System.

Keyless Entry Keypad

The keyless entry keypad is hardwired to the BCM (Body Control Module). The BCM (Body Control Module) interprets the inputs from the keyless entry keypad and then controls the associated operation. The keyless entry keypad is illuminated for 5 seconds when any button is pressed. The BCM (Body Control Module) requests the illuminated entry feature to turn the interior lamps on when a valid entry code is received. If a lock all doors code is entered, the illuminated entry feature turns off.

NOTE: The keyless entry keypad does not lock the doors if the driver door is ajar.

The keyless entry keypad supplies a signal to the BCM (Body Control Module) when the buttons are pressed. The BCM (Body Control Module) then supplies voltage to the appropriate door lock actuator(s) to lock or unlock the doors or release the liftgate (vehicles equipped with a manual liftgate). On vehicles with memory, the keyless entry keypad also causes the BCM (Body Control Module) to send an MS-CAN (Medium Speed Controller Area Network) message to the DSM (Driver Seat Module) to activate all memory features to the positions associated with the personal entry code entered in on the keypad.

Field-Effect Transistor (FET) Protection

Field-Effect Transistor (FET) is a type of transistor that, when used with module software, monitors and controls current flow on module outputs. The FET (Field-Effect Transistor) protection strategy prevents module damage in the event of excessive current flow.

The BCM (Body Control Module) utilizes a FET (Field-Effect Transistor) protective circuit strategy for many of its outputs (for example, a headlamp output circuit). Output loads (current level) are monitored for excessive current (typically short circuits) and are shut down (turns off the voltage or ground provided by the module) when a fault event is detected. A short circuit DTC is stored at the fault event and a cumulative counter is started.

When the demand for the output is no longer present, the module resets the FET (Field-Effect Transistor) circuit protection to allow the circuit to function. The next time the driver requests a circuit to activate that has been shut down by a previous short (FET (Field-Effect Transistor) protection) and the circuit is still shorted, the FET (Field-Effect Transistor) protection shuts off the circuit again and the cumulative counter advances.

When the excessive circuit load occurs often enough, the module shuts down the output until a repair procedure is carried out. Each FET (Field-Effect Transistor) protected circuit has 3 predefined levels of short circuit tolerance based on the harmful effect of each circuit fault on the FET (Field-Effect Transistor) and the ability of the FET (Field-Effect Transistor) to withstand it. A module lifetime level of fault events is established based upon the durability of the FET (Field-Effect Transistor). If the total tolerance level is determined to be 600 fault events, the 3 predefined levels would be 200, 400 and 600 fault events.

When each tolerance level is reached, the short circuit DTC that was stored on the first failure cannot be cleared by a command to clear the continuous DTCs. The module does not allow this code to be cleared or the circuit restored to normal operation until a successful self-test proves that the fault has been repaired. After the self-test has successfully completed (no on-demand DTCs present), DTC U1000:00 and the associated DTC (the DTC related to the shorted circuit) automatically clears and the circuit function returns.

When each level is reached, the DTC associated with the short circuit sets along with DTC U1000:00. These DTCs can be cleared using the module on-demand self-test, then the Clear DTC operation on the scan tool (if the on-demand test shows the fault corrected). The module never resets the fault event counter to zero and continues to advance the fault event counter as short circuit fault events occur.

If the number of short circuit fault events reach the third level, then DTCs U1000:00 and U3000:49 set along with the associated short circuit DTC. DTC U3000:49 cannot be cleared and the module must be replaced after the repair.

The BCM (Body Control Module) utilizes FET (Field-Effect Transistor) protected output circuit for the handles, locks, and latches system is the keypad illumination output circuit.