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Old 09-10-2015, 04:21 PM
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Replacing the PCM

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Old 12-06-2009, 08:23 AM   #1
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Default Replacing the PCM

1995 Cherokee 4.0 manual. not starting, had a diagnostic at the local dealer and they told me it was the pcm. they wanted $600, and more than $200 to install it. I picked one up at a wrecking yard and want to know if i can check to make sure it is functional or what is required to sync it with my jeep?
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Old 12-06-2009, 08:53 AM   #2
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just undo the 5/16 bolt holding the harness to your original pcm, then just unplug the harness and plug it into the replacement computer and see if the jeep will start. if it seems fine, then unbolt the original computer and bolt in the new one. don't forget the bolt to hold the harness in place.

you can swap out the computer in about 10 minutes. junkyards have them for under 100 bux.

don't forget to unhook the battery before you attempt to undo your computer tho. and don't hook it back up for about 10 minutes after you plug in the new pcm.
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Old 12-06-2009, 09:17 AM   #3
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Ok i have done that. it is still not starting so it was either not the pcm, or the one i got from the junkyard is also faulty?
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Old 12-06-2009, 09:28 AM   #4
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Quote:
Originally Posted by jeepete View Post
Ok i have done that. it is still not starting so it was either not the pcm, or the one i got from the junkyard is also faulty?
not likley the pcm, poor diagnosis. Have you had the cps checked? the basics, spark, fuel?
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Old 12-06-2009, 09:44 AM   #5
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i replaced the CPS before i had the diagnostic, have intermittent spark at the coil, no spark from the distributor also new; wires, plugs, cap, rotor, CMP
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Old 12-06-2009, 04:33 PM   #6
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Where is the pcm located on a 96, i cant find it or dont know what im looking for i guess. any help appreciated thanks
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Old 12-06-2009, 10:28 PM   #7
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drivers side inner fender. has a big wiring harness attached to it with a bolt in the center of it.

looks like this

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Old 08-26-2010, 04:03 PM   #8
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I am having trouble finding a pcm for my 1994 jeep grand cherokee limited 4.0 4x4 automatic. Any ideas
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Old 08-26-2010, 10:46 PM   #9
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tones of them in the junkyards. around here anyways.

as for the location of the pcm, it's kinda tucked away and hidden on the passenger side inner fender/firewall under the hood.
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Old 08-29-2010, 01:19 AM   #10
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what if any are signs you may need a new one? I can't figure my studdering, sensor changing codes, badly running XJ out.
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Old 03-05-2011, 05:33 PM   #11
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how can u tell its ur PCM?
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Old 03-05-2011, 05:44 PM   #12
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Quote:
Originally Posted by jeepete View Post
i replaced the CPS before i had the diagnostic, have intermittent spark at the coil, no spark from the distributor also new; wires, plugs, cap, rotor, CMP
Lets go back to the original post....

Did you test or replace your ignition coil? Freshen ALL engine grounds? The ASD (autoshutdown) system still in play too.

More on the ASD below.

Spark: 12 volts from ignition switch to the ASD relay; when the key is first turned on the PCM provides a ground to the ASD relay to energize it, then the ASD relay passes 12 volts to the coil primary side. If no crank sensor signal is generated after a couple of seconds the PCM cuts the ground to the ASD relay (and fuel pump relay too) and that cuts power to the coil (and fuel pump). Key to START and once again the PCM energizes the ASD relay. Now, a critical element is the crank sensor--no signal from the crank sensor and the PCM won't trigger the coil to provide spark.

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Old 04-25-2011, 09:05 PM   #13
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on the same subject. what if the PCM needing to be replaced is the wrong match for the Cherokee? I am thinking that may be the case for mine. I'm either the 3rd or 4th owner of my '95 Sport.
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Old 05-03-2011, 11:40 AM   #14
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Bump. Anyone?
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Old 05-03-2011, 11:59 AM   #15
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maybe call a ecm place might help theres lot of one for your year maybe vin will helphttp://www.autocomputersystems.com/index.php

Last edited by freegdr; 05-03-2011 at 12:01 PM.
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