Principles Of Operation

Handles, Locks, Latches and Entry Systems

Principles of Operation

The Remote Function Actuator (RFA) module receives inputs and delivers outputs to many of the electronically controlled features of the vehicle. The RFA module constantly monitors the system under its control and reports an issue in the form of a DTC.

Power Door Locks

Regardless of the key position, the RFA module and the Driver Door Module (DDM) are supplied voltage at all times. When the RFA module receives a signal from the Intelligent Access (IA) key through the Remote Functions Receiver (RFR) module, the keyless entry keypad, or the RH door lock control switch, it sends a ground signal to the lock and unlock relays. When the LH door lock control switch is pressed, the DDM receives the lock or unlock signal. The DDM sends a request through the Medium Speed Controller Area Network (MS-CAN) to the RFA module to lock or unlock the doors.

Driver Door Intelligent Access (IA) Feature

The driver door IA feature allows the driver door to be unlocked without having to use the door lock cylinder or the Remote Keyless Entry (RKE) transmitter. With a programmed IA key within 1 m (3 ft) of the driver door handle outside of the driver door, touch any button on the keyless entry keypad, and the driver door unlocks (with stepped unlock enabled), or unlocks all doors (if stepped unlock is disabled). When the RFA module detects keyless entry keypad activity, it activates the low frequency antenna in the driver door handle. The low frequency antenna sends out a signal to the IA key. The low frequency signal activates the IA key and the IA key then sends a high frequency signal back to the RFR module. The RFR module interprets the high frequency signal from the IA key and sends the information to the RFA module. If the RFA module determines that it is a programmed key, it unlocks the driver door or all doors.

Liftgate Intelligent Access (IA) Feature

The liftgate IA feature allows the liftgate to be opened without having to use the interior liftgate open/close switch or the keyless entry keypad. With a programmed IA key within 1 m (3 ft) outside of the liftgate, press the exterior liftgate switch on the rear bumper cover, and the liftgate opens. When the RFA module detects a signal from the exterior liftgate switch, it activates the low frequency antenna in the rear bumper cover. The low frequency antenna sends out a signal to the IA key. The low frequency signal activates the IA key and the IA key then sends a high frequency signal back to the RFR module. The RFR module interprets the high frequency signal from the IA key and sends the information to the RFA module. If the RFA module determines that it is a programmed key, it sends voltage to the Liftgate/Trunk Module (LTM). When the LTM detects the voltage indicating an open request, it opens the liftgate. For operation of the power liftgate and it components, refer to Doors, Hood and Trunk.

Remote Keyless Entry (RKE)

The RFA module interprets radio frequency signals from the IA key transmitters. The RFA 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 IA key transmitter supplies a signal to the RFR module when any button is pressed. The RFR module interprets the information from the IA key and then sends a signal to the RFA module. The RFA module then supplies voltage to the appropriate door lock actuator(s) to lock or unlock the doors or open/close the liftgate. The IA key can also be used to activate the panic alarm.

The RKE feature also causes the RFA module to send an MS-CAN message to the Driver Seat Module (DSM) to activate all memory features to the positions associated with the IA key being used.

Keyless Entry Keypad

The keyless entry keypad is hardwired to the RFA module. The RFA 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 and when the courtesy lighting is illuminated or 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 RFA module when the buttons are touched. The RFA module then supplies voltage to the appropriate door lock actuator(s) to lock or unlock the doors or open the liftgate. The keyless entry keypad also causes the RFA module to send an MS-CAN message to the DSM to activate all memory features to the positions associated with the personal entry code entered on the keypad.

Field-Effect Transistor (FET) Protection

Field-Effect Transistor (FET) is a type of transistor that when used with module software can be used to monitor and control current flow on module outputs. The FET protection strategy is used to prevent module damage in the event of excessive current flow.

The RFA module utilizes a FET 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 continuous 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 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 protection) and the circuit remains shorted, the FET 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 protected circuit has 3 predefined levels of short circuit tolerance based on the harmful effect of each circuit fault on the FET and the ability of the FET to withstand it. A module lifetime level of fault events is established based upon the durability of the FET. 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 continuous 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 continuous DTC (the DTC related to the shorted circuit) automatically clears and the circuit function returns.

When the first or second level is reached, the continuous 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 DTC U3000:49 sets along with the associated continuous DTC. This DTC cannot be cleared and the module must be replaced.

The only RFA module FET protected output circuit for the handles, locks, latches and entry systems is the keypad illumination circuit.