Principles of Operation

PRINCIPLES OF OPERATION

Power Locks
The power lock/unlock feature requests all of the vehicle doors to lock or unlock upon a request from the door lock control switch, keyless entry keypad, or remote keyless entry (RKE) transmitter. Power locking and unlocking functions independently of the key position, vehicle speed, or transmission position. The vehicle security module (VSM) activates internal relays to supply the correct powers and grounds for the door lock actuators.

Remote Keyless Entry (RKE) Transmitter
The RKE transmitter can be programmed using a scan tool or by using the ignition lock cylinder method.

The RKE transmitter initiates the following electronic system functions:
- Unlocks the driver door
- Unlocks all doors
- Locks all doors
- Activates/deactivates the panic alarm
- Commands the interior lamps on (when unlocking) and off (when locking)
- Flashes the parking lamps once when LOCK is pressed once and all the doors are closed
- If any door is ajar, the parking lamps will not flash when LOCK is pressed until all doors are closed
- Sounds the horn once and flashes the parking lamps once when LOCK is pressed twice within 3 seconds and the doors are closed
- Sounds the horn twice if the LOCK is pressed twice within 3 seconds if any door is ajar

The RKE transmitter has a normal operating range of 10 m (33 ft).

Keyless Entry Keypad
The keyless entry keypad, located in the exterior handle of the driver door, provides a method for the customer to access the vehicle without a key or RKE transmitter. The keyless entry keypad feature:
- locks all doors and inhibits the door lock control switch unlock capability after 20 seconds (if the inhibit feature is enabled).
- unlocks only the driver door.
- unlocks all doors.
- programs/erases the customer key code.
- enables/disables autolocking.

The keyless entry keypad feature operates independently of key position status, vehicle speed, or transmission position. When a keyless entry keypad button is pressed, the keyless entry keypad buttons illuminate to provide better visibility. If LOCK ALL DOORS is entered or 5 seconds have elapsed since the last button press, the illumination is turned off.

Each vehicle equipped with a keyless entry keypad is programmed with a permanent factory 5-digit keyless entry keypad code. This code is provided to the customer through a wallet card in the Owner's Literature package. In addition, this code is available through a scan tool and is also printed on the VSM label. When entering customer or permanent codes, each digit must be entered within 5 seconds of the previous button press.

Field-Effect Transistor (FET) Protection
The VSM utilizes a FET protective circuit strategy for only one of its outputs (horn). 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 is detected. A continuous DTC is stored at that time for the fault. The circuit will then reset after a customer demand of the function (switching the component on). When an excessive circuit load occurs several times, the module shuts down the output until a repair procedure is carried out. At the same time, 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 until a successful on-demand self-test proves that the fault has been repaired. After the on-demand self-test has successfully completed (no on-demand DTCs present), the continuous DTC clears and the circuit function returns.

Each circuit has 3 predefined levels of short circuit tolerance established in the module based on each circuits capability. When the first or second level is reached, the continuous DTC associated with the circuit sets along with DTC B106E. These DTCs may be cleared using the Clear DTC operation on the scan tool as long as the fault itself has been corrected. If any of the circuits are shorted past the third level, then B1342 sets along with the associated continuous DTC. This DTC cannot be cleared and the module must be replaced.

The horn circuit 1 (DB) is the only FET protected circuit.