Principles of Operation (How Does It Work?)

NOTE: The Front Electronic Module (FEM), Rear Electronic Module (REM), and the Remote Keyless Entry (RKE) must all be reconfigured before installing a new module. REFER to Information Bus.

The RKE (Driver Door Module) (DDM)) receives inputs from the remote transmitter(s) and delivers the outputs through the Standard Corporate Protocol (SCP) communication network. This allows the driver to lock and unlock the vehicles power lock system (if equipped). The RKE (DDM) can be programmed to accept up to four individual Transmitter Identification Codes (TIC) from four different remote transmitters. The RKE (DDM) constantly monitors the systems under its control and reports a concern in the form of Diagnostic Trouble Codes (DTCs). A DTC can be retrieved using a New Generation STAR (NGS) tester by connecting it to the Data Link Connector (DLC).

The vehicle's electronic functions are divided into zones. The FEM controls the front portion of the vehicle and the REM controls the rear portion of the vehicle. These systems rely heavily on the SCP communication network in order to transmit and receive signals. As a technician, it is very important to understand:
^ where the input (command) originates from
^ All information (messages) necessary in order for a feature to operate
^ which module(s) receive(s) the input or command message
^ does the module which received the input (message), control the output of the feature, or does it output a message over the SCP communication network to another module
^ which module controls the output of the feature.

The RKE Driver Door Module (DDM) processes messages from the remote transmitter and outputs the messages to other modules. Some of the messages include:
^ the power door locks (if equipped)
^ the power sliding door interface (if equipped)
^ the anti-theft perimeter protection alarm
^ which module controls the output of the feature

The power door locks are controlled by the FEM, REM, and RKE (DDM). The FEM and REM receive messages from the RKE (DDM) over the SCP communication network. The FEM is hardwired to the driver door and controls the locking functions of this door only. The REM is hardwired to all of the other doors and controls all locking functions of these doors including the liftgate. All power door locks are powered by the Switched System Power (SSP) function. A failure of any or all of the SSP features could cause inoperative power door lock functions. When diagnosing the power door lock systems, it is essential to determine if all related DTCs are controlled by the SSP feature. The remote door locking system can be disabled also if the ignition or PRNDL messages are not being received by the RKE module. The REM is hardwired to the Left Passenger Side Door Module (LPSDM) and the Right Passenger Side Door Modules (RPSDM). The LPSDM and the RPSDM talks with the REM to determine if the passenger side door(s) can be opened. The information the REM is looking for is PRNDL position from the Powertrain Control Module (PCM), vehicle speed from the anti-lock brake control module, and the remote transmitter signal from the RKE (DDM). The LPSDM and the RPSDM have pre-conditions to meet before the side doors can be opened. These modules look for a vehicle speed of less than 6 mph, the vehicle is in PARK, a remote transmitter sent a open signal or a open signal was received from the passenger side door switch. To close a side door only a close signal from the passenger side door switch or from the remote transmitter is needed. The vehicle speed signal and the PRNDL signal is ignored at this point.

The remote transmitters and the RKE (DDM) use a rolling code to prevent the TIC codes from being "captured" by a code grabber. The system rolls the counter in the transmitter and in the RKE (DDM) every time a remote transmitter button is pressed. If the remote transmitter button is pressed outside the range of the vehicle the rolling codes will fail to synchronize and the vehicle will stop responding to that remote transmitter. At this point the transmitter needs to be reprogrammed to the system.

The smart lock system is designed to keep the driver from locking the keys within the vehicle. The FEM does this by unlocking the doors, if the driver locks the doors while the key is in the off position and is still in the ignition, and a door is open. The doors will lock and then unlock. The auto-lock system is designed to lock all the doors once the vehicle begins to move. A couple of conditions have to be met. All the doors have to be closed, the key in the RUN position, the transmission transitions out of PARK, and the vehicle speed is greater then 5 mph.

The SSP is invoked by both the FEM and REM. This function removes power from relays that provide power to the exterior lamps, interior lamps, and power door locks. This is only accomplished when both the FEM and the REM are in sleep mode. The sleep function of the FEM and REM places the modules in sleep mode when the ignition switch is in the OFF position, and no wake up (inputs) signals occur for 30 minutes. The module will not sleep if the parking lamps or the hazard lamps are active. The following relays are controlled by the SSP function: SSP1, SSP2, SSP3, and SSP4. When either the FEM or REM are not in sleep mode, all SSP relays will be energized. Each relay, when energized, will supply power to multiple features/functions. Refer to the SSP Index for diagnosis and testing of SSP related issues. Component Tests and General Diagnostics