95 ZJ security system "Power Up Alarm Mode"

[Muddzz]

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?

 

[ZJTROY]

When this happens unlock the door with the key, it should disable the alarm system. My 95 5.2 does this all the time

 

[Muddzz]

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.

 

[nicolas5]

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

 

[nicolas5]

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.

 

[RERJR]

I just joined to respond to this topic of what I'll call the "Jeep 3 second kill" because I've learned a lot from and other Jeep forums about the problem I just experienced with our 1993 Grand Cherokee w/ 4Lthat I bought used in Nov of 2000 and more than doubled the miles on it now showing 263373 miles, and I feel like I owe it to others to share what I have learned.

Like so many responders it gave me fits after starting it up for the first time this spring and for the first time ever gave me the dreaded "3 second kill" ---- over and over and over with no fault codes except the 55 no codes. I'm a retired mechanic from the pre-computer days so when we bought our first Jeep (also used, a 1990 Cherokee Laredo that went 390,00 before rusting away) I bought the factory shop manual to get comfortable with the computer controlled ignition and multi-port injection, and also for our two later used Jeeps, 1993 and 1996 Jeep Grands, all w/ 4L and all w/ 4wd and 4speed auto.

FYI If you happen to own a 1993, like the one I mention here Jeep switched auto trannys early in 1993 from a Borg Warner to the Legacy Torque Flite 904 after designing a 4th gear addition in front of the tail shaft and published an additional volume to their shop manual for the new tranny; since called the "42RE". But they didn't revise the original manual so there a few mysteries in it, especially in the electronics.

Long story, short as possible; after reading many ideas I tested sensors and replaced questionable ones, including a complete new distributor including the cam sensor, which also operates the injectors, in spite of the code 55 because it was original and needed a cap and rotor anyway. And by then I determined that the problem was caused by the injectors losing ground from the PCM after switch from "start" to "run". Didn't the crank sensor, though some contributors suggested it, but did replace the coil because the kill problem reminded me of symptoms when the coil did once fail. I didn't ground the famous V/Y wires because I don't like short cuts unless my life somehow depends on it. (conclusion up next)

After dog-earing many pages in the shop manual back and forth to fuel and ignition pages I realized that the anti-theft included a "shutdown" function, which I had forgotten, probably because after all the years we've owned it I've never triggered it w/o being able to disarm it with lock-unlock with the ignition key or fob (simple fob in 1993, only lock-unlock). So recalling there was a trouble-shoot process in section 8W in the Jeep shop manual I rotated the key from OFF to ACC. (opposite from trouble codes Off to RUN) and wow, all alarms went off including the horn and lights, which I quick disabled with the fob, and thinking "Ah Rats, the theft alarm isn't the problem so I'll call it a day and refresh my tired mind with beer and a good night's sleep."

But out of habit formed over the past many days I cranked it again before exiting, counted the seconds and sure enough it was purring like new. Though still wondering why, I backtracked my work and what I had learned and experienced;
1) As the manual said, the horn didn't sound when I tripped the alarm with the hood up to connect the battery cables, only the headlights and I quickly disabled manually with the key. But CLUE ONE, when I later closed the hood switch with a clamp and took the battery cable off on again the horn didn't sound as it should have, just the lights. I've tried all door switches and fob and they all disarmed the headlight.
2) It was only after triggering the alarm by the test procedure; the key from OFF to ACC. a couple times, that the horn and headlights blasted and after that the disarm using the fob (that did previously disarm the light function as well) allowed the engine to start.
3) My assumption is that there are two separate components, or circuits, to the alarm system that must be disabled at the same time, one must activate/deactivate the lights and the other the horn before the PCM sends ground signals to the injectors.

My plan is to check the wiring in the front right door that disarms with the key but not the fob. But in the mean time the Jeep runs and starts again just fine and have put several miles on it since, and if it happens again I can simply disarm it with the test procedure OFF to ACC a couple times. As complicated as the complete ignition system is; if a reader is having this problem it may not be for the same cause, even if the injectors loose ground from the PCM, but the test procedure OFF to ACC. a couple times is free and anyone can conduct it. Thanks to all who have commented on this subject and I hope my addition can help at least some before they decide "to throw their Jeep in the lake" as one writer posted.