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post #1 of (permalink) Old 07-18-2009, 08:03 PM Thread Starter
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94 YJ PCM Pin desc?

Anyone out there have a schematic, or a decriptions of the pin locations for a 94 yj PCM?

My PCM is just not working, PCM is good, want to make sure grounds and power is too.

Thanks

Scott
1985 CJ7 T.H.O.R

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-Psalm 40:2
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post #2 of (permalink) Old 07-19-2009, 02:12 PM
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Not off hand, but I do know that pins 11 and 12 are grounds. When you check them, don't use an ohm meter, use a high load test light hooked to B+. These grounds carry the load of the ign module and are usually the source of failure.
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post #3 of (permalink) Old 07-19-2009, 05:58 PM
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I have an 1994 OEM YJ shop manual. I don't have a scanner or I would shoot you a page. The diagram I will refer to is on page 8W-141. I could make photo copy and snail mail it to you

Pin for battery is pin/cavety #3, you also have two ignition pins, pin 9 is start/run, and pin 19 is just ignition.

Dorfs nailed this one, pins for deadicated source ground, are pins 11 & 12.

To access your pins to do tests, have the connector attached to the ecm and pin numbers should be viewable on the wire end of the connector.

Hope this helps.

1985 CJ with a transplanted 94YJ 4.0L motor, T176 tranny, mainly stock otherwise. ><>

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post #4 of (permalink) Old 07-20-2009, 01:10 PM Thread Starter
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Quote:
When you check them, don't use an ohm meter, use a high load test light hooked to B+
Could you explain? I have 12.5v going through both grounds, and what I believe to be always hot.

Scott
1985 CJ7 T.H.O.R

"He brought me up out of the pit of destruction, out of the miry clay, And He set my feet upon a rock making my footsteps firm."
-Psalm 40:2
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post #5 of (permalink) Old 07-20-2009, 01:23 PM Thread Starter
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BTW: The 1994 Wrangler repair manual is here:
Jeep 1994 Wrangler Service Manual free download,schematics,datasheets,eeprom bins,pcb,repair info for test equipment and electronics

and Here:
Jeep 1994 Wrangler Service Manual free download,schematics,datasheets,eeprom bins,pcb,repair info for test equipment and electronics

There are 19 parts to the rar file, it is ~ 59m when done.

Scott
1985 CJ7 T.H.O.R

"He brought me up out of the pit of destruction, out of the miry clay, And He set my feet upon a rock making my footsteps firm."
-Psalm 40:2
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post #6 of (permalink) Old 07-20-2009, 01:34 PM Thread Starter
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It says it is 1994, but it is for a 2004 TJ, oh well.

Scott
1985 CJ7 T.H.O.R

"He brought me up out of the pit of destruction, out of the miry clay, And He set my feet upon a rock making my footsteps firm."
-Psalm 40:2
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post #7 of (permalink) Old 07-20-2009, 01:56 PM Thread Starter
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Ok, found a '95 YJ wiring diagram online here:

Jeep 1995 YJ - FSM Wiring Diagrams

Here is the PCM.

Duane, could you do me a great favor and verify it is the same as your '94 FSM?
Thanks Much.
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File Type: jpg 95YJPCM.jpg (79.4 KB, 9 views)

Scott
1985 CJ7 T.H.O.R

"He brought me up out of the pit of destruction, out of the miry clay, And He set my feet upon a rock making my footsteps firm."
-Psalm 40:2
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post #8 of (permalink) Old 07-20-2009, 04:44 PM
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With the PCM disconnected, hook the battery up. Clip the end of your test light to B+, so every time you touch the probe to a fender or grounded part of the car it lights. Then probe pins 11 and 12. The test light should light brightly. The bigger the test light the better, in fact Chrysler recomends using a headlight for a test light. This will simulate the high load of the ignition circuit. This circuit is a high failure one. I would almost recommend running another heavy ground wire to both of these wires. I believe that about 2 or 3 feet up the harness these two wires break out of the harness and ground through a 10 mm bolt to the fender. Another ground to look for is the heavy eyelet that attaches to the dip stick hold down bolt, I think it is part of the same ground.
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post #9 of (permalink) Old 07-20-2009, 09:30 PM
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Quote:
Originally Posted by thorjeep View Post
Ok, found a '95 YJ wiring diagram online here:

Jeep 1995 YJ - FSM Wiring Diagrams

Here is the PCM.

Duane, could you do me a great favor and verify it is the same as your '94 FSM?
Thanks Much.
Ok Scott, here it goes, now remember I am not a Chrylser Jeep Master Service Tech

To answer your question, it is not the same

I refering to page 8W-141 (YJ section schemtic 64)
Below are the labeling differences I found by cavity (what my 94 manual says).
CAV 3 - Battery
CAV 5 - Sensor for Fuel
CAV 6 - Sensor Return
CAV 7 - Vehicle Speed Sensor Mag (+)
CAV 9 - Ignition I start & run
CAV 24 - Vehicle Speed Sensor Mag (-)
CAV 25 - Data Link
CAV 29 - TCC Feed (brake)
CAV 45 - Data Link
CAV 51 - Fuel Pump Relay Coil
CAV 57 - ASD Battery Sense

The rest pretty much else line up with my manual. Hope this helps

1985 CJ with a transplanted 94YJ 4.0L motor, T176 tranny, mainly stock otherwise. ><>
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post #10 of (permalink) Old 07-20-2009, 10:26 PM
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Quote:
Originally Posted by dorfs View Post
The bigger the test light the better, in fact Chrysler recomends using a headlight for a test light.
In a series circuit, the voltage divides proportional to the resistances. A high impedance (meaning high resistance) VOM will show full voltage even with another resistance, like a bad connection, in series.

The headlight bulb has low resistance and a large voltage drop will occur across any bad connections.

There are 10 kinds of people in the world.
Those who understand binary and those who don't.
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