Resetting 1997 ZG Jeep Immobiliser ??

[incairns1]

I recently parked my 1997 Jeep Laredo. only to find it just never to start again, It would crank over but just not start. After several tests by my ex 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.??

During this whole process I had to get a new battery also.
I have the key fob that works but I think it may be the engine imobiliser. 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.

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

[Doctor W]

I don't think it was the original PSM, I think it's the immobiliser.

The New PCM won't work with your immobiliser/fob either. You can't just fit them in, they need programming I think.

Put the old PCM back and before hooking up battery, join NEG treminal to battery FIRST.....then hold POS terminal to battery NEG for 15 seconds or so.......then unhook NEG terminal and connect POS terminal to battery POS, then connect NEG term. to NEG post.

The red flashing light of immobiliser should be going Y/N?......press fob control to unlock (Do you hear doors unlock? does red flasher go off???......if not the fob isn't working, fit new batteries in it. If doors unlock and flasher goes off, then try to start car.........If it still won't start you need an EXPERT!! A good Jeep Mechanic/Electrician who has a Jeep DRB tool/scanner!........If it does.......It may need to be revved a liitle bit as PCM has had it's learning memory wiped and idle may be too slow for a few minutes.

Good Luck!

ALSO, THIS Q IS IN THE WRONG SECTION.....MOVE IT TO GRAND CHEROKEES OR TECHNICAL Q'S

[incairns1]

I have had the Grand for 8 years now and never seen any flashing light on the dash ?? However the key fob has always worked and still does works fine except befor the exchanged pcm the engine would crank over and over (as if no spark) then when putting in the replacement pcm, it now fires up perfectly but dies after 2 seconds. Also the Panic button does not activate anything anymore, it used to work fine???
I appreciate you help

[Doctor W]

There's a flashing LED on top of dash, on LHS (sitting in driver's seat) of car......it flashes as long as immobiliser is active.