How It Works

The fob has three push buttons: LOCK, UNLOCK, and ALERT. When a button is pushed, the fob sends a radio frequency signal to the ECM. The signal contains a unique vehicle access code that identifies the individual fob, plus codes that indicate which button has been pushed.

The ECM detects the signal sent by the fob, amplifies it, and converts it to a digital sequence.

If the LOCK button is pressed, the ECM arms the system. It locks the two cab doors, begins to monitor all the entry points (the two cab doors, the sleeper cab access door, and the two baggage doors, as installed), and instructs the relay module to start flashing the system LED at the slow rate. If any entry points are open, the ECM sounds the horn and flashes the cab marker lights twice. If the ignition keyswitch is turned off, the ECM interrupts ignition power to the engine.

The driver may be inside or outside the vehicle. However, if the engine is running at the time the LOCK button is pressed, the system still enters the armed state, except that the engine is not immobilized. This improves security for the occupant as well as comfort while sleeping or resting, because the system is armed, and the heating or air conditioning is operating without draining any batteries.

Once the system is armed, the alarm functions activate whenever one of the entry points is opened. In the alarmed state, the ECM does the following:

• Immobilizes the vehicle by cutting off power between the ignition keyswitch and the engine electronic control unit (ECU).

• Sounds the horn in pulses of 0.5 second on, 0.5 second off.

• Flashes the cab marker lights in pulses of 0.5 second on, 0.5 second off.

• Changes the blink rate of the LED from slow to fast.

If the UNLOCK button is pressed, the ECM disarms the system, if armed. It unlocks all the entry points, discontinues its monitoring of the entry points, instructs the relay module to stop flashing the system LED, and restores ignition power to the engine, if interrupted.

If the ALERT button is pressed, the ECM executes the unlock sequence and also activates the vehicle alarm functions (see above). To cancel an ALERT (to turn off the alarm), press the UNLOCK button.

Once activated, the alarm sequence continues for 30 seconds unless deactivated by pressing the UNLOCK button on the fob. After 30 seconds in the alarmed state, the system automatically enters the violated state.

In the violated state, the horn does not sound and the cab marker lights do not flash, but the engine is still immobilized and the LED continues to blink at the fast rate. The vehicle remains in this state until the UNLOCK button is pressed.