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95 ZJ security system "Power Up Alarm Mode"

Muddzz

NAXJA Forum User
Location
USA
I have a 95 ZJ Limited with an OEM passive security system and was helping a friend work on his Jeep, with my rear hatch open for access to tools, etc.


The entire day the rear hatch was opened and I went to start the ZJ at the end of the day and the headlights started flashing and the engine wouldn't start.


There was some sound which sounded like the solenoid making a noise, but could not here the starter turning.


I thought perhaps the battery was low without enough power to turn the starter. So we tried jumping the battery and also connecting a battery charger but the same thing occurred, headlight flashing, and the engine would not start.


Turning on the headlights, they were on steady and bright.


I couldn't figure out what the problem was such as low battery, security system preventing engine from starting or other?



So I left the battery charger on for several of hours and then came back to try to start the engine and the same thing occurred.


So this last time I kept on cranking the engine which after ~30 second or longer the engine started.



The engine was running just fine so I stopped and tried starting again without any problems. 4.0L now starts very quickly as before.


I'm still wondering the cause of the problem such as low battery, loose connection, etc. causing the passive security system to detect a battery disconnect and putting itself in a Power Up Alarm Mode.


From the Theft and Security FSM I'm finding


Power up alarm mode. When the battery is disconnected and reconnected the security system enters into a power up alarm mode.

- Flashes headlight
- Flashes Park and taillights
- Prevents the engine from starting.
__________

In order to prevent the engine from starting the PCM disables the fuel injectors fuel delivery (fuel injectors pulse).


So I'm thinking the security system did go into a power up alarm mode but am perplexed of the cause. Can a low batter effect the passive security system causing it to put itself into a power up alarm mode?


Or the cause is a loose and/or corroded wire or plug-in that's part of the security system battery monitoring?
 
When this happens unlock the door with the key, it should disable the alarm system. My 95 5.2 does this all the time


That's not normal. It' means the PCM and VSS is sensing a battery disconnect and then reconnect.


It happened when I left my doors open for a full day. I assumed the battery had become low and then connected a charger for a few hours and it didn't occur after charging up the battery.



I haven't had time to experiment such as installing a low charged battery to verify there's a problem when the battery become low or another problem.


The VSS should only go into "Power Up Alarm Mode" when the battery is completely disconnected and then reconnected.
 
That's not normal. It' means the PCM and VSS is sensing a battery disconnect and then reconnect.


It happened when I left my doors open for a full day. I assumed the battery had become low and then connected a charger for a few hours and it didn't occur after charging up the battery.



I haven't had time to experiment such as installing a low charged battery to verify there's a problem when the battery become low or another problem.


The VSS should only go into "Power Up Alarm Mode" when the battery is completely disconnected and then reconnected.
Thanks for share good informetion
 
When this happens unlock the door with the key, it should disable the alarm system. My 95 5.2 does this all the time
Thank you for sharing your experience! Unlocking the door with the key to disable the alarm system is a common workaround for many vehicles. It's a useful tip for owners encountering similar issues with their alarm systems.
 
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