Power Locks: Description and Operation

The power lock system allows all of the doors to be locked or unlocked electrically by operating a switch on either front door trim panel. The power lock system receives non-switched battery current through a fuse in the Integrated Power Module (IPM), so that the power locks remain operational, regardless of the ignition switch position.

The Body Control Module (BCM) locks the doors automatically when the vehicle is driven beyond the speed of 25.7 Km/h (15 mph), all doors are closed, the accelerator pedal is depressed and the door lock actuation had not been previously activated. The rolling door lock feature is customer programmable.

This vehicle also offers several customer programmable features, which allows the selection of several optional electronic features to suit individual preferences.

The power lock system for this vehicle can also be operated remotely using the available Remote Keyless Entry (RKE) system radio frequency transmitters, if equipped.

AUTOMATIC DOOR LOCKS
When enabled, this feature will lock all of the door locks if all of the doors are closed and the vehicle speed goes above 25.7 km/h (15 mph). If a door unlock has occurred, then the BCM will perform another auto lock, if the doors did not electrically unlock, another auto lock will not occur.

DOOR LOCK INHIBIT
When the key is in the ignition (in any switch position) and either front door is opened, the door lock switches LOCK functions are disabled. The UN-LOCK functions are still functional. This protects against locking the vehicle with the key still in the ignition. The RKE key fob will still lock the doors. After the key is removed from the ignition or the doors are closed, the power door locks will operate normally.

REMOTE KEYLESS ENTRY
The Remote Keyless Entry (RKE) system allows the use of a remote battery-powered radio transmitter to communicate with the BCM to actuate the power lock system.

The RKE transmitters are also equipped with a Panic button. If the Panic button on the RKE transmitter is depressed, the horn will sound and the exterior lights will flash on the vehicle for about three minutes, or until the Panic button is depressed a second time. Pressing the Panic button also activates the courtesy lamps. Pressing the Panic button again stops the exterior lamps from flashing and the horn from sounding. However, the courtesy lamps will remain illuminated until either the BCM times out lamp operation or until the turning of the ignition. The panic feature will operate if the ignition is ON, but only if the Panic button is pressed prior to starting the vehicle. A vehicle speed of about 25.7 km/h (15 miles-per-hour) will also cancel the panic event.

The RKE system can also perform other functions on this vehicle. If the vehicle is equipped with the optional Vehicle Theft Security System (VTSS), the RKE transmitter will arm the VTSS when the Lock button is depressed, and disarm the VTSS when the Unlock button is depressed.

The RKE system includes two transmitters when the vehicle is shipped from the factory, but the system can retain the vehicle access codes of up to a total of eight transmitters. If an RKE transmitter is inoperative or lost, new transmitter vehicle access codes can be programmed into the system using a DRB III (R) scan tool.

This vehicle also offers several customer programmable features, which allows the selection of several optional electronic features to suit individual preferences. Customer programmable feature options affecting the RKE system include:
- Automatic Door Lock - Customer programmable feature that allows the BCM to perform an automatic door lock if the vehicle speed is above 25.7 km/h (15 miles-per-hour).
- Automatic Door Unlock On Exit - Customer programmable feature that allows the BCM to perform an automatic door unlock if the vehicle speed is 0, vehicle in park and driver door is opened.
- Flash Lights with Lock and Unlock -Allows the option of having the park lamps flash as an optical verification that the RKE system received a valid Lock request or Unlock request from the RKE transmitter, or having no optical verification.
- Programming Additional Transmitters -Allows up to a total of four transmitter vehicle access codes to be stored.
- Remote Unlock Sequence - Allows the option of having only the driver side front door unlock when the RKE transmitter Unlock button is depressed the first time. The remaining doors unlock when the button is depressed a second time within 5 seconds of the first unlock press. Another option is having all doors unlock upon the first depression of the RKE transmitter Unlock button.
- Sound Horn on Lock - Allows the option of having the horn sound a short chirp as an audible verification that the RKE system received a valid

Lock request from the RKE transmitter, or having no audible verification.

The Body Control Module (BCM) locks or unlocks the doors when an actuation input signal from a door lock switch, Central Lock key cylinder or Remote Keyless Entry (RKE) is received. The BCM turns on the output drivers and provides a voltage level to the door lock motor for a specified time.

REMOTE KEYLESS ENTRY
The RKE transmitter uses radio frequency signals to communicate with the SKREEM module. The SKREEM is on the PCI bus. When the operator presses a button on the transmitter, it sends a specific request to the SKREEM. In turn, the SKREEM sends the appropriate request over the PCI bus to the following:
- Integrated Power Module (IPM) - to activate the park lamps, the headlamps and the horn for the horn chirp.
- Power Liftgate Module (PLGM) - to control the liftgate lock and unlock functions.

After pressing the lock button on the RKE transmitter, all of the door locks will lock, the illuminated entry will turn off (if all doors are closed) and the vehicle theft security system (if equipped) will arm.

Pressing the unlock button one time will unlock the driver door, or all doors based on the customer programmable feature enabled, the illuminated entry will turn on the courtesy lamps and the vehicle theft security system (if equipped) will disarm. Pressing the unlock button a second time, the remaining door locks will unlock.

If the vehicle is equipped with the memory system, the memory message will identify which transmitter (1 or 2) sent the signal.

ROLLING CODE
The rolling code feature changes part of the transmitter message each time that it is used. The transmitter message and the receiver message increment together. Under certain conditions with a rolling code system, such as pressing a button on the RKE transmitter over 255 times outside of receiver range or replacing the battery, the receiver and transmitter can fall out of synchronization. To re-synchronize, press and release the UNLOCK button on the RKE transmitter repeatedly (it may take up to eight cycles) while listening carefully for the power door locks in the vehicle to cycle, indicating that resynchronization has occurred.

The lock function works from the RKE transmitter even in an out of synchronization condition, therefore it could be verified by pressing the LOCK button on the RKE key fob.