SOS! 911! Jeep Guru’s Please Help!! Factory Security - 2 JY PCM – No Start - JeepForum.com
 
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post #1 of 11 Old 10-14-2015, 04:42 AM Thread Starter
Al222
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SOS! 911! Jeep Guru’s Please Help!! Factory Security - 2 JY PCM – No Start

Hi all,

Let me start out by saying that I have read more than 40 hours on every Jeep Dodge website I could find. I have talked to multiple certified mechanics. I have been troubleshooting for over 2 months, and I could sincerely use some help.

95 Jeep Grand Cherokee 5.2 Laredo

Problem: When the key is energized in the “On” position, “Initially,” there is no power to the fuel pump. CEL is not illuminated. If you leave the key in the On position for 7-30 minutes. Eventually the ASD relay will start clicking, extremely LOUD clicking. ASD relay clicks for 25-35 seconds. Then the fuel pump relay starts clicking loudly 10-20 seconds. After the relays stop clicking the fuel pump runs. The engine starts as normal.

Note: It runs with the original PCM, but you have to leave the key in the On position for 7-30 minutes before starting.

Research has shown that many people have solved this problem with a junkyard PCM.

I have tried 2 separate junkyard PCMs. Both PCMs act exactly the same way. When the key is energized to the “On” position, CEL light comes on normally, the fuel pump runs normally. But, the engine will not start. Turn key off, turn key On = fuel pump runs normally. No start.

Note: Both replacement PCM stopped all relay clicking.

Note: The interior lights have not worked since 1999 – Fuse #5 blows. Also, the hood open switch/light bulb is unplugged.

Note: When resetting the PCM. I disconnect the positive cable from the battery. Ground the positive and negative cable together for 30 seconds. Reconnect the pos cable. Turn key on, but do not start. Turn headlights on. Turn headlights off. Turn key off.

Without going into 2 months of troubleshooting...

My question is, could the factory security system prevent junkyard PCMs from starting the engine? If this is a security related problem is there a way to disable the security system when installing a new PCM?

Also, could this be a CPS issue with the new PCMs? If this is a crank position sensor problem, why does the engine run with the old PCM?

Thank you and greatly appreciated!!

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post #2 of 11 Old 10-14-2015, 05:28 AM
coralman
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Doesn't the hood open switch have something to do with the alarm?

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lol...if life is as a simple as a 5.9 making you happy, I'd say go ahead and buy it on impulse. ZJs are the way of Zen. Wax on, wax off
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post #3 of 11 Old 10-14-2015, 06:28 AM
PolkaPower
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Quote:
Originally Posted by coralman View Post
Doesn't the hood open switch have something to do with the alarm?
On my 95 the hood alarm plunger on the drivers side of the hood had a bent plastic part. I had to put cardboard under it to keep the alarm from randomly going off.
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post #4 of 11 Old 10-14-2015, 06:38 AM
ZeeJay1997
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The capacitors in the PCM are weak. The 93 and 94 can be recapped
easily, not sure about the 95.

With JY PCMs everything has to match including security on a 95. Maybe a model year / drivetrain mismatch?

Once again, I'm not sure about the 95, but on the 93 and 94 the security module can be removed while it's running and you never worry about security again.

The 95s are a transition year and are akin Frankenstein in regards to the electronics.

It's not the crank sensor.


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post #5 of 11 Old 10-14-2015, 08:24 AM Thread Starter
Al222
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Quote:
Originally Posted by ZeeJay1997 View Post
The capacitors in the PCM are weak. The 93 and 94 can be recapped
easily, not sure about the 95.

With JY PCMs everything has to match including security on a 95. Maybe a model year / drivetrain mismatch?

Once again, I'm not sure about the 95, but on the 93 and 94 the security module can be removed while it's running and you never worry about security again.

The 95s are a transition year and are akin Frankenstein in regards to the electronics.

It's not the crank sensor.
ZeeJay1997,

First of all, thank you for responding. I have spent hours reading your posts. Glad to hear it's not the CPS.

We bought it in 1999 from a used car dealership. It appears the security module was removed before we bought it.

As a shot in the dark I removed the following fuses:
Fuse #4 Security lamp
Fuse #6 Security Alarm Module
Fuse #7 Security Alarm Relay, Security Alarm Module, Flash to Pass
Fuse #21 Security Alarm Module, Lamp Outage Module
Circuit Breaker #27 Security Alarm Module and Front Wiper

Reset PCM
It started for 2 seconds. Then it would spit and spudder, but no start.

Removed VTSS Relay
Reset PCM
It started for 2 seconds. Then it would spit and spudder, but no start.

I will double check that the PCM came from a 95 JGC Lareado.

Other than checking on the donor PCM, Am I missing something?
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post #6 of 11 Old 10-14-2015, 11:39 AM
ZeeJay1997
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Apparently the 95 is like the 93 and 94 in regards to the security system. It is a single shot analog signal from the security module to the PCM to set the security mode. Once it's in either the "engine no start" or "engine run" mode it's stuck there regardless of battery disconnect. The PCMs from the yard need a security module to tell the PCM to start the engine. You can go back to the yard and get a security module and it will probably do the trick.

Once the PCM is in the engine run mode, you can take the security module out (while engine is running) again if you like. There's probably a reason someone removed the security module from your vehicle and personally, I would ask if I could return the module before I left the yard with it.

Note for science... the above is not true for 96 and up.


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post #7 of 11 Old 10-14-2015, 12:41 PM
BRULE
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93 grand wagoneer start -auto shutdown

i had fought with the start and auto shut down issue for many many exhausting hours - do this - do that - pull fuses - pull relays - undo battery you name it i did it -- had to leave jeep many times as it would not continue to run after it easily fired up -- well somewhere i read about turning the key to the accesory position three times - the horn automatically honks and the jeep starts right up and runs -- that must erase some codes or something along those lines - anyways what a relief now i am on the road everyday with no worries ....
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post #8 of 11 Old 10-14-2015, 01:06 PM
Luke4010
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Since your original ECM will start and run the vehicle, it would be best to recap it rather than mess around with the security module.
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post #9 of 11 Old 10-14-2015, 02:15 PM
ZeeJay1997
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Quote:
Originally Posted by Luke4010 View Post
Since your original ECM will start and run the vehicle, it would be best to recap it rather than mess around with the security module.
Agreed that option is still on the table. I'm not familiar with the innards of a 95 PCM when compared to the 93-94. The recapping write states that it doesn't apply to the 95-98. If it can't be easily resolved by installing a security module, it would be worth a shot IMO. After all the PCM is bad so there's nothing to lose.


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post #10 of 11 Old 10-14-2015, 02:20 PM
ZeeJay1997
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After a brief search, I find that the 95 can be recapped and has been done successfully.

https://www.jeepforum.com/forum/f13/f...l#post18515601


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post #11 of 11 Old 10-14-2015, 03:47 PM
kg6mov
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Its only the second gen PCM that can't be recapped.


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