Diagnostic Mode

A diagnostics mode is available in the system to verify operation of all monitored switches or circuits. System self-tests can be entered only with the DRB.

Upon entering diagnostics, the headlamps, park, and tail lamps will begin flashing to verify their operation. In addition, the horn will sound twice. Returning the ignition to the OFF position will stop the lamps from flashing while keeping the system in diagnostics.





While in diagnostics mode, a horn pulse should occur at each of the following events, which indicates proper operation. (Note that some vehicles equipped with the vehicle theft security system are also equipped with illuminated entry (see chart). When in diagnostic mode, it is recommended that the illuminated entry relay be removed.

1. Beginning with all doors closed, open, then close each door. The horn will sound when the door jamb/ajar switch closes, and then again when the switch opens. There must be a 1-second delay between closing and opening the switch.
2. Activate the power door locks in both the lock and unlock directions. The horn will sound after each activation.
3. Rotate the key in each door lock cylinder to the unlock position. The horn will sound as the switch closes, and again when it opens. There must be a 1-second delay between changing switch states, or the horn will not sound.
4. Activate the remote keyless entry in both the lock and unlock directions. The horn will sound after each activation.
5. Cycle the key to the ignition RUN position. A single horn pulse will indicate proper operation of the ignition input. This also will take the module out of the diagnostics mode.

For any of these tests, if the switch does not remain open or closed for at least 1 second, the horn will only sound once.

The lack of a horn pulse during any operation indicates either:

- a switch failure
- the lack of that input to the vehicle theft security system module
- a failure internal to the module

Check for continuity at the switch. If this is good, check for an open or shorted wire between the switch and alarm module. Also, check if the Powertrain Control Module (PCM) has been replaced recently. For the first 20 engine starts with a new PCM, the vehicle theft security system will function normally except it will not prevent the engine from running.

NOTE: A PCM from a vehicle equipped with a vehicle theft security system (VTSS) cannot be used in a vehicle that is not equipped with a vehicle theft security system.

If the VTSS indicator lamp comes on and stays on after the ignition has been placed in the ON position, the CCD bus communication with the powertrain control module possibly has been lost.