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Unread 07-16-2013, 08:10 PM   #16
ladydrac24
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1994 FSJ Cherokee 
 
Join Date: Jul 2013
Location: norcross, Georgia
Posts: 17
not sure what one of these the pcm would be

fc6562b.jpg

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Unread 07-16-2013, 08:18 PM   #17
ZeeJay1997
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1997 ZJ 
 
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Location: Sweet Home, Alabama
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check the small 20A eng ctrl and 30a large eng ctrl.

PCM = Engine Control Unit or ECU

you are welcome
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Unread 07-16-2013, 08:29 PM   #18
ladydrac24
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1994 FSJ Cherokee 
 
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Location: norcross, Georgia
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All the fuses are fine so i guess that means the PCM that is the power train control mod right
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Unread 07-16-2013, 08:39 PM   #19
ZeeJay1997
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If you have the resources to do so, you need to pull the connector off the PCM and check for voltage at the connector with the switch on. It's for assurance that it's not a broken wire between the fusebox and PCM, and that you didnt overlook a blown fuse.

You need to check between pin 3 and 5, 3 and 11, and 3 and 12. Should read battery voltage on all.
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Unread 07-16-2013, 08:45 PM   #20
MyKeyB
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1997 ZJ 
 
Join Date: Feb 2013
Location: Youngstown, Ohio
Posts: 300
PCM = power control module.
Or computer or brain box. Sounds like the capacitors might be bad. It looks like an easy fix if you or a friend can solder. There is a great post here on how to fix it. Id search for it and post the link but right Im on my phone and that sucks to do. Search the forum for computer cap replacement and you should find the thread.
__________________
Rust never sleeps...
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Unread 07-19-2013, 07:45 AM   #21
ladydrac24
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1994 FSJ Cherokee 
 
Join Date: Jul 2013
Location: norcross, Georgia
Posts: 17
ok replaced the PCM and still the same thing. all it does is do a yeng, yeng,yeng, sound. no check engine light is on all fuses, and relays are fine. any ideas what else it could be.
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Unread 07-19-2013, 07:52 AM   #22
dellis
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1998 ZJ 
 
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Did you do what ZeeJay suggested about 3 posts above, checking to ensure you have good power to your PCM?
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Unread 07-19-2013, 08:38 AM   #23
ZeeJay1997
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We really need to know if the PCM is getting power, but if you don't have the ability to do so you can shoot in the dark and may get lucky.

Something i should have added earlier, a sensor can short out and cause the PCM to have no output without blowing a fuse.

Disconnect O2 and crank sensors and see if PCM will do CEL bulb check at key ON. Those are the most common, but other could be having the same effect.

The crank sensor connector is on passenger side of the block near the firewall close to the Y in the big harness. it is a three wire connector out by itself and the pigtail goes over the top of the bellhousing.

The O2 connector is on the drivers side below the manifolds and the harness should be bolted to the side of the block. Just find the sensor on the manifold and follow the wire forward.

Both of these have lock mechanisms that you have to get past to disconnect.
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Unread 07-19-2013, 11:17 AM   #24
ladydrac24
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Location: norcross, Georgia
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Yes I did the test and the PCM is getting Full Power will try the crank sen and o2 connector
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Unread 07-19-2013, 11:26 AM   #25
ZeeJay1997
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If disconnecting one of those doesnt make the CEL come back to life, check the ignition switch input to the PCM connector, Pin 9
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Unread 07-28-2013, 02:49 PM   #26
ladydrac24
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1994 FSJ Cherokee 
 
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Location: norcross, Georgia
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ok still needing help my jeep will nit start. we disconnceted the ingnition coil and tested it and it is fine how ever when we conncet it to the jeep it is not giving a spark what could be wrong
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Unread 07-28-2013, 07:17 PM   #27
ZeeJay1997
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did you try disconnect the 2 sensors to see if the CEL started working again?
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Unread 07-29-2013, 06:24 PM   #28
ladydrac24
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1994 FSJ Cherokee 
 
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ok did the test again on the PCM got power on 3 to 9 3 to 11 and 3 to 12 but not at 3 to five. we have replaced the crankshaft sensor already any idea why the jeep still is not sparking at the ignition coil????
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Unread 07-29-2013, 06:52 PM   #29
ZeeJay1997
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Quote:
Originally Posted by ladydrac24 View Post
ok did the test again on the PCM got power on 3 to 9 3 to 11 and 3 to 12 but not at 3 to five. we have replaced the crankshaft sensor already any idea why the jeep still is not sparking at the ignition coil????
With the switch on you should get battery voltage from pin 9 to battery ground. This is the juice from the ignition switch. i imagine you checked from 3 to 9 with switch off, therefore you read battery voltage. if the switch was off this is a normal reading, but we still dont know if the PCM is getting ignition signal

It sounds like one of your grounds is missing. To confirm, 11 and 12 (grounds) should read zero ohms to battery negative and read zero ohms to each other.
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Unread 07-29-2013, 06:56 PM   #30
ZeeJay1997
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Disregard last post, I had the wrong engine... ooops

Your grounds check good.

I still need you to go from 9 to negative post with switch on and see if it is getting battery voltage there.
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