Anti-theft / Alarm diagnostics

[95zj-tilshedies]

I have read a lot of threads on this and other forums written by people trying to diagnose various gremlins in their anti-theft systems. I came across this self-diagnostic procedure in my FSM over the weekend, and was able to pinpoint the issues that have been bugging me since I bought my ZJ.

Keep in mind that this procedure is from the FSM for a '95. The anti-theft systems in these vehicles are IR (infrared) controlled. I am pretty sure that that changed in '96, and the systems were RC (radio controlled). I would imagine that this procedure would work for GC's prior to 1996, but I can't bet the pink slip on it.
BTW: VTA = Vehicle Theft Alarm

SELF-DIAGNOSIS
A self-diagnosis mode is available in the VTA system
to verify operation of all monitored switches or
circuits. To enter this mode, cycle the ignition switch
ACCESSORY-OFF-ACCESSORY-OFF-ACCESSORY,
leaving the switch in the ACCESSORY position.
Upon entering the self-diagnosis mode 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 the diagnostic mode.
Also note that vehicles equipped with VTA are
equipped with the illuminated entry system. When in
the diagnostic mode it is recommended that the illuminated
entry relay be removed. Otherwise, it is necessary
to wait 30 second for the illuminated entry
system to time out after each door opening or closure.
While in the diagnostic mode, a horn pulse should
occur at each of the following events indicating
proper operation. However, if a switch is cycled too
quickly and does not remain open or closed for at
least 1 second, the horn will not sound to confirm operation.
(1) Beginning with all doors closed, open then close
each door. The horn will sound when the door jamb
switch closes, and 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.
(4) Rotate the key in each door lock cylinder to the
lock position, then 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.
(5) Activate the remote keyless entry in both the
lock and unlock directions. The horn will sound after
each activation.
(6) Cycle the ignition key to the ignition switch ON
position. A single horn pulse will indicate proper operation
of the ignition input. This also will take the
module out of the diagnostic mode.
The lack of a horn pulse response to any of the
above tests indicates:

• a switch failure
• an open or shorted circuit between the switch and the VTA module
• an internal VTA module failure.

Check for continuity at the switch. If OK, check for
an open or shorted wire between the switch and VTA
module. Also, check if the powertrain control module
(PCM) has been replaced recently. For the first 20
engine starts with a new PCM, the VTA will function
normally except for the engine no-run feature.
A PCM from a vehicle equipped with VTA cannot
be used in a vehicle that is not equipped
with VTA.
If the security lamp comes on after ignition
ON and stays on, the CCD bus communication
with the PCM has been lost.


I was able to identify a bad door disarm switch in my driver's door that wouldn't let me deactivate the alarm with the key (only with the key fob).

I hope that this helps someone, and remember that I have only been able to confirm that this works on my '95. If anyone else has success, please reply and let the forum know.