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Jeep Grand Cherokee Security System

Q. Hi Vince; How are you? My 1994 Jeep Grand Cherokee (ZJ) has an alarm problem. When I set the alarm by knobs in the door handle, the alarm goes off. It goes off either after ½-hour, or after maybe up to 8 to 10 hours. This is without any one trying to break in or anything. I have followed the process to set the alarm properly, and it seems that it get set properly.

Jeep Grand Cherokee Security System

The security light inside the dash blinks for few seconds and then goes off and all the door are locked. Also the panel inside the car that shows some failure modes and warning signs, like door ajar, tailgate light, etc.., sometimes flashes, especially when the alarm goes off, but also gives wrong message, like tailgate light not working.

I have checked the tailgate light and it is okay. But looks like the light was old. When I changed it the warning light went away, but came back a day later. The battery is about four years old, it is a five year battery. The connections are clean and okay. Looks like there is very small crack in one terminal, it is not noticeable anyways.

The remote was not working properly, so I changed the battery. I can not lock all the car with remote, but can open it when the car is locked with keys or from inside. I have following questions:

  1. What do you think is the problem, Am I setting the alarm properly. I have been doing this for past 7 years, so it seems I have been doing it right.
  2. How can I disable the security systems? I am afraid if that is a problem, it would cost me an arm and a leg to replace any electronic module like security system, so If I can disable, I can live without it.
  3. Is the security alarm and the warning signal panel underneath the dash interconnected, it seems that way to me.
  4. Is there a way to replace or repair the security system myself.

Thanks,
Fred

A. A diagnostics mode is available in the system to verify operation of all monitored switches or circuits. To enter diagnostics without the DRB, cycle the ignition key to the accessory position three times, leaving the key in this position.

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.

Jeep Grand Cherokee Security System

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. Otherwise it is necessary to wait for the 30 seconds delay after each door opening or closure.)

  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. Open, then close the hood. The horn will sound when the hood is opened, and again when it is closed.
  3. Activate the power door locks in both the lock and unlock directions. The horn will sound after each activation (except Viper).
  4. Rotate the key in each door lock cylinder to the unlock position (except Viper). 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.
  5. Activate the remote keyless entry in both the lock and unlock directions. The horn will sound after each activation.
  6. 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.

This will help you pinpoint the problem. If not, you will need to get the service manual, you can get it at the Public Library in the Reference Section, and use the diagnostic procedure with the wiring diagram to track it down.

Jeep Grand Cherokee Security System

If you just want to disable it, unplugging the VTSS module will disable the system.

Additional Information provided courtesy of AllDATA

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