I recently parked my 1997 ZG Jeep Laredo 4 lt Petrol. only to find it just never to start again, It would crank over but just not start. After several tests by my mechanic neighbour. He was 100% sure I had a faulty PCM. I purchased a second hand pcm with same numbers out of a running vehicle. Now it starts perfectly for 2 seconds then shut down.?? (with the old pcm it would not start at all)

During this whole process I had to get a new battery also.
The key fob (black key) works fine, but I think it may be the engine immobiliser ?. shutting the engine down. I have also disconnected the battery to drain any charge and hopefully reset the pcm and/or enable the immobiliser. This did nothing.

I have no flashing red light on dash (never have had)

I had an Auto electrician out with his scanner and he could not work out the problem and left saying "he would have to do a little research" (that was 4 weeks ago.He's not coming back!!)

Can somebody please help me with this issue in getting my only transport up and running again.

 

It's in theft mode, you need the dealer to flash program the PCM.

 

i have just baught a 97 jeep cherokee and it has been standing for 4 years in a garage.
the owner said it would start on the button at christmas and the remotes where working fine back then.
when i got it the battery was knackered so i replaced it.
i have hade the remotes checked and they are giving a signal but they wont lock or unlock the doors.
the jeep starts and stops but thats it.
is there any way i can bypass the little black box under the dash???
i know this is a thatchem approved sytem and bypasses the original control unit that was fitted to the vehicle..
i am a VW commercial master tech so i know a bit about electrics but i have no wiring diagrams and have no idea about the systems jeep use so i would love some help and support from anyone who might know what to do...
kind regards to you all.

mark

 

Bruce! (I mean Mark) You need to hit the "new thread" button! (you will find that after clicking "oem cherokee tech", above). Incairns1, not to differ with Bustedback, (I have plenty to learn yet) ....There's a deal, your PCM will ground the ASD relay for a couple secs when you turn on the key, also cranking I think. THEN, when it gets the right signals you are running it will continue grounding that crucial relay to keep power going to things like the ignition and injectors.

Now it's foggy....if a wire to the 02 sensor grounds it blows which fuse which results in what...?? Sorry. (mine doesn't so that). Check the fuses, even the "mini" ones in the PDC under the hood. (and the wires to the 02 sensors) Just my .02.

 

Hello, get the zj running yet? sounds like it is in "vtss" one easy way to disarm if you don't have a factory keyless transmitter....look at the following pic....cut the disarm wire and ground it (computer side) this will disable the vtss and prevent it from happening again.
Good luck

 

:smokin:

YASSIR! That is exactly correct!

hope he reads it! it will alleviate many future hassles.

cpnwrench

:smokin:

 

thanks all for your help i will try your advice at the weekend and let you know how i get on....... thanks again.... cheers!!

 

If I had to guess, the PCM you bought was originally in a vehicle with the SENTRY key system. The only way I know of to properly fix that problem is having the PCM flashed and the SENTRY programming removed. The replacement PCM needs to be flashed for your VIN number and mileage anyway, so you might as well have it done at the same time.