Bandonbound

Still nothing on the 93 Cherokee. Have eliminated, I think, the security system as its working like it should. Arm, dissarm etc. New Clue! I did try a donor ECU box yesterday, does not have the security system mode but worth a try. Still nothing, BUT, did give me the CEL lite and able to scan it, well with the key but is that a clue? My original ECU shows no CEL on startup and can't get codes with key on off 5x's system. Is that a clue for someone out there?? Thanks David in Ca

Creature85

What year and model is the spare ECU from? What exactly did you do to test the security system?

Mudtallica

Had the same issues in my '98.. Sounds like the CPS..

Bandonbound

Thanks for the interest. The donor box is from a running driving 94 Cherokee without security. Got only one thing out of installing it and that was now have CEL on the dash and can key check the codes. No codes.
Security system checked and rechecked. Dissarms with all three locks, reset it 10x. Locked with door panel lock, closed door, checked dash lite and its flashing, on and on. Totally removed security module yesterday and no difference., Thanks for any more input! David in Ca.

Creature85

I know you said that it acts the same (no start) with the spare ECU but did you check afterwards to make sure you still didn't have spark or fuel pressure? As Mudtallica stated it could also be the CPS giving you grief. Here's a decent write up on how to check if yours is working properly.

https://www.cherokeeforum.com/f51/testing-cps-5563/