Hello,
So I've been baffled trying to figure this out. Maybe someone might know if I missed something. I have a 1996 Jeep Cherokee Sport 4.0L 173K miles. It did have a check engine light on previously but ran fine for a while. Well recently it had been having starting issues intermittently or stalling while driving. I did replace the camshaft sensor and the ignition coil and that seemed to do the trick for the stalling while driving. Well then a different issue came about where it would run and drive fine but once parked it randomly would get a "crank, no start" issue. Well I would unplug the battery and reset the computer and give it some time and would be OK again for a while. This time it finally went out for good. Was getting no spark, no fuel nothing. I've replaced almost everything I've read and could think of, crankshaft sensor, fuel pump, relays, fuses, camshaft sensor, ignition coil. Plug wires and distributor were done a couple years ago. Went to plug in a code reader and was getting nothing from the computer. So I did go ahead and change out the PCM. I ended up getting a Cardone 79-1199 re manufactured unit from O'Reilly. My unit I pulled out was 56041199 and it looked like this unit from Cardone was programmed for that model as well.



I did have better luck with that, fuel pressure and spark is there. However it does try to start but will not stay running. I plugged in my reader and I see where all the oxygen sensors, 02, heat are bad and catalytic converter is crap, which I knew and knew I needed to replace but it never effected it before. My question is with all the emission sensors bad would that prevent it from running? Or was this PCM unit possibly no good?

https://www.cardone.com/product/engi...mputer-79-1199

 

Did the OBDll reader work on the original PCM before this? I know that some readers just don't work on my Jeep. It really sounds like a ground issue. These Jeeps do all sort of whacky electrical/not running things because of bad grounds. Cruiser has some great tips on this at https://cruiser54.com/. As far as running with bad O2 sensors, I do not believe there is a auto shut down for that....it will just run like crap.
Hope this helps

 

I did have it at a shop a couple months ago and their reader did work. The one I used could not read, but one of the things I read on here too was when the Gen light and Check engine light both stop coming on then there's an issue with the PCM. So when I put the new one in both Gen and Check engine did come back on and everything seemed to register fine, I don't see any codes pop up with this new PCM in other than bad 02 but then again I haven't even got it to run yet. I will say it's always had a odd electrical draw, like slow wiper blades, the cabin fan sounded slower. What ground wires would be good to check? I did notice one towards the back of the block looked caked in grease and made me wonder.

 

lots here

grease is good, but fully clean and check those 2 earth points, one of them is PCM earth !

You need a '96 compliant scanner, I got a BAFX for about $30. its always fitted, uses Torque Lite (free) mobile App

try and free download the '96 manual

New non-oem O2 sensors are often bad, try disconnecting it completely

199 is correct for a ;96 PCM

Does the voltage gauge show over 12V ? ie is the Alt working, confirm with multimeter, PCM regulates it

You can use the Live Data to read voltage..a bad connection meant mine was not regulating, no code, had voltage, but alt light was on

Does the fuel pump audibly prime for 3 secs when key is turned to "on"

You can listen to ASD and fuel pump relays