Security anti-theft issue
 

01 Grand Cherokee Limited
4.0L and
140k miles

Hi all. My problem first became apparent when the dash gauges would act sporadically while driving. I found that the negative cable was loose in the terminal and tightened it. This happened as I was just about to leave state for three months of training. While away, my wife was driving it when the same symptoms happened again. She was able to get it home, and I had a friend replace the negative cable. Ever since then the Jeep will do the "run for 2 seconds" thing and shut off. Since we also have a Dakota, she just drives that and the Jeep sits in the backyard. As an OTR truck driver now, I'm haven't been home often enough to worry too much about having the second vehicle, but I need to get it running simply because it's worth it.
When I was home last, I towed it to the dealer. They said the PCM was bad, and quoted me $900 to fix it. Instead, I ordered a pre-programmed "plug n play" PCM off the internet and popped it in yesterday. However, it still shuts off after a couple seconds. No change from beforeI've tried all the so-called fix it resets I can find, but nothing is working. I'm not sure where to proceed.

Any codes?
What's the fuel pressure in psi?
Have you tried replacing the ignition switch yet?

No codes showing but I'm not sure it would since the battery had been disconnected so many times recently.
I don't have a way at the moment to check the fuel pressure, but it starts and runs great for the few seconds before cutting out.
No ignition switch. All I've done so far is replace the ecm. Other than that I've just tried the various immobilizer reset remedies, but none have worked.

Regarding the ignition, if I replace the SKIM do I need to replace the ignition lock too? This is all new to me so I'm learning as I go.

i am having the same issue did you ever get this resolved

Yes, but it may not be the same way you want to fix your problem. I took the new PCM that I just purchased and sent it to https://store.allcomputerresources.com/

For $100 (includes shipping both ways) they disabled the SKIM immobilizer from the PCM, so the Jeep will run now and I'll never have that problem again. The security key symbol on the dash still comes on, but it doesn't affect the Jeep now. I can deal with that key symbol by putting a piece of tape over it lol. I just needed the Jeep to run.

I think that same company will sell a reman PCM with the skim disabled but since I already had the new PCM I just sent it.

My problem was probably just a bad SKIM module from the get-go, shorted out by a faulty battery connection initially. For less than 200 I could have replaced that, but I opted to eliminate the immobilizer altogether so it never happens again.

If you opt to go this route also, make sure you unplug the skim module located in the steering column before you install the new PCM. I was told to do that so that the new PCM won't read a faulty skim anymore. That's what I did, and it worked.

For that matter, in hindsight I don't know for sure that my original PCM was bad to begin with. The dealer told me it was, but who knows. If your PCM is still good you can just send it to that company instead of buying a new one. They don't repair bad PCMs,, but they will deprogram the immobilizer from a good one.

My 95 ZJ 4.0L came with what is called a Passive Security System, which does have some control over the ignition and engine starting.

I'm uncertain if it's the same for your security system which may have an immobilizer which immobilizes engine starting through the ignition key and
cylinder.

A passive security system basically has sensors for the doors, door locks, hood, hatch, ignition, key fob, electric door locks, etc. When a sensor is tripped while the passive security system is armed an alarm is sound with flashing lights. One of the features is the passive security system will prevent an engine from running by disabling the fuel injectors, engine may start and then immediately be turned off due to an security alarm, such as tampering with door locks, ignition, etc. while the passive security system is armed.

However there is another scenario where the passive security system will disable the fuel injectors (preventing an engine from running).

When battery is disconnected and then reconnected the passive security system will go into a "Power Up Alarm Mode"

From: Vehicle Theft Security FSM

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 (pulse).

So it's possible the Passive Security System is reading a battery disconnect and then reconnect.

This happened in my 95 ZJ once I wasn't able to start the 4.0L. I'm uncertain of the cause such as low battery, loose wire, corrosion, plug-in, etc. effecting the monitoring of the battery voltage by the Passive Security System and PCM.

From what you described it's possible your security system is going into some sort of mode that disables the fuel injectors immediately after your engine has started. In order to prevent someone from driving away.

This sort of thing happened once on my 95 ZJ only I wasn't able to start the engine.

Don't know if this helps, but on my 97 the door switches become disabled (stuck or broken) on the front doors or rear hatch. This can play havoc with the security system. Pretty easy to diagnose and replace just 2 wire switch to tell the bcm if you're locked or unlocked. If they stick in the locked position and you try to start the car it will do the shut down thing.