So I just put a PCM in my grand cherokee and now it wont start... it ran with the old one, but the check engine light was on and they said it was throwing two codes for the PCM so I took it to try and get it flashed and that was a waste so I ordered one... is there something else I have to do aside from disconnect the battery, disconnect the old one, plug in the new one, and reconnect the battery?
96 grand cherokee limited PCM issue
- Thread starter zig8121
- Start date
MudderChuck
New member
There is a re learn procedure for a new PCM, you are likely going to need a FSM. I don't have the procedure for the grand.
I'd clean the connectors up well. One thing to avoid is flashing the PCM by wiggling the battery terminals. Wiggling the battery terminals can result in a low charge condition, maybe worse. Just a guess, but I'd also hook up all the PCM connections before hooking up the battery. I've had pins back out of a connector before, grab each wire carefully and tug a little. If one does back out, spread the lock tab a little (carefully) and shove it back in there all the way.
I think you may have other issues besides the PCM, sometimes codes will fool you. A fairly common problem is a partial short in the CPS, in the non test side (the two poles not covered in the quick test in the book). It may suck down the voltage to the sync (cam) sensor and cause all sorts of grief and has never thrown a true code I've ever seen.
A quick test is to turn the key to run and see if the fuel pump relay closes for a few seconds (normal prime). Then turn to start and see if the fuel pump relay closes again during start. You can also test for spark during start. Your ASD relay may not be closing during start, there can be a few reasons for this, sensor or wiring, PCM or even your anti theft module.
I'd clean the connectors up well. One thing to avoid is flashing the PCM by wiggling the battery terminals. Wiggling the battery terminals can result in a low charge condition, maybe worse. Just a guess, but I'd also hook up all the PCM connections before hooking up the battery. I've had pins back out of a connector before, grab each wire carefully and tug a little. If one does back out, spread the lock tab a little (carefully) and shove it back in there all the way.
I think you may have other issues besides the PCM, sometimes codes will fool you. A fairly common problem is a partial short in the CPS, in the non test side (the two poles not covered in the quick test in the book). It may suck down the voltage to the sync (cam) sensor and cause all sorts of grief and has never thrown a true code I've ever seen.
A quick test is to turn the key to run and see if the fuel pump relay closes for a few seconds (normal prime). Then turn to start and see if the fuel pump relay closes again during start. You can also test for spark during start. Your ASD relay may not be closing during start, there can be a few reasons for this, sensor or wiring, PCM or even your anti theft module.
alright well I found out the main problem was they sent me the wrong computer, there's two PCMs for the same exact jeep, so I finally got the right one and it starts with the new one but it runs rich as hell, it shakes, and the check engine light is still on... do I need to wait till it goes through a drive cycle so it can adjust or does it still sound like something else is still wrong that I'm missing? the only two codes it was throwing for the check enging light were both for the PCM so I'm not getting why it wouldnt go off with a new PCM.
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