I have a 1995 YJi with a 4.0. I don't have power to the pcm, no spark at the spark plugs and no power at the injectors. Im at a loss.... could someone help? Thanks joey
No power to the pcm
Jmoesch
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As @WICruiser said, start tracing backwards. Could have a shorted wire or other issue. Possible the ASD relay is causing issues too.
Thank you, what I have is a 95 yj with a 2.5 with a 5 speed, I swap it with a 1997 tj engine and transmission with a 4.0 with a 5 speed. I changed the injector to a 95 with other sensors so that the 95 wiring harness will fit. The only computer that I could find is out of a 1995 Cherokee with a auto transmissions. The wiring harness is in good shape an I'm think that the computer is bad. I'm going to try to ck it today! However I'm not to sure how to go about it? Any imput?
Ok, I have been checking some this morning. Is the 1995 and 1997 ring tone on the flywheel different? I have power to the crankshaft sensor. One side on the connector is bright and the other side is dim and the center is nothing? Not sure how to ck to see if it is working right
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There are some differences in the harness pin-outs between a 4-cyl and 6-cyl...
On the body harness connector C107, the 2.5L harness provides circuit K7 (18OR) with a 8V supply from pin #7 from the ECM. This is what provides 8V+ for the crank sensor (at splice 115), cam sensor and vehicle speed sensor (at splice 121). Between Splice #115 (near the crank position sensor), K7 goes through C107 and then to C105 before going to the cam and other sensors (the 5V+ supply that feeds the MAP and TPS sensor is from PCM pin#6).
On the 4.0L harness, circuit K7 does NOT go through the C107 connector and is instead directly wired from C139 (the connector at the PCM) to splice #115 and out to the sensor (splice #115 on the harness serves the same function as splice #115 and #121 on the 4-cyl harness).
It is likely that if you're using the 4-cyl body harness that you'll need to rewire (or add a bridge circuit) the pinout of C107 to the K7 circuit somewhere along the harness (mimicking the 4.0L harness 8V supply).
Thank you. I have a 1995 wiring harness and I have changed all sensors to fit the 1995 harness. I have power to everything but the coil! Further testing on the computer, pin 19 (ignition) no power! That's telling me the computer is bad? What are your thoughts?
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I believe Pin 19 is the coil driver side, meaning the PCM uses pin 19 to ground the coil, completing the circuit and energizing the coil. I believe this is how it adjusts the timing depending on engine load and parameters.
Power to the coil, as well as injectors, should also feed power to Pin 57 as a sense circuit...
If you have power to the coil (+ side), you should also have power to the injectors as these are fed off the same splice. I would work your way back through the harness and make sure you didn't miss a clip or repin.
Did you happen to change your body harness as well? If not, the harness by the battery has a different pin output (mentioned above) and this could be your issue as there is a connector prior to the splice on the 4-cyl models.
Power to the coil, as well as injectors, should also feed power to Pin 57 as a sense circuit...
If you have power to the coil (+ side), you should also have power to the injectors as these are fed off the same splice. I would work your way back through the harness and make sure you didn't miss a clip or repin.
Did you happen to change your body harness as well? If not, the harness by the battery has a different pin output (mentioned above) and this could be your issue as there is a connector prior to the splice on the 4-cyl models.
It is telling me you need a basic understanding how the system before replacing the most expensive part
That pin on the PCM is the coil driver but it drives the coil with a pulsing GROUND it NEVER has power
The coil also gets a constant plus 12 on its other wire
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That pin on the PCM is the coil driver but it drives the coil with a pulsing GROUND it NEVER has power
The coil also gets a constant plus 12 on its other wire
Sent from my iPod touch using Tapatalk
Thank you for your help. Yes you are right. I have a 4.0 engine harness and a 2.5 body harness. I understand what you are saying however I'm not sure which wire i should tie into what wire. I'm looking at the diagram that you sent me. And I'm trying to understand it. And thank you again.
Where was the ground wire unplugged at ?
where was this ground wire disconnected at?
Welcome to the Forum @Nbowles93
Jmoesch hasn't been on the forum in almost a year. It's unlikely you'll get a response.
Your best bet is to begin your own thread. Describe your Jeep (year, engine/trans and any mods you know about). Then describe your problem and any attempts at diagnosis and/or repair.
Here's a link we often refer new members to...
www.wranglerforum.com
Good Luck, L.M.
Jmoesch hasn't been on the forum in almost a year. It's unlikely you'll get a response.
Your best bet is to begin your own thread. Describe your Jeep (year, engine/trans and any mods you know about). Then describe your problem and any attempts at diagnosis and/or repair.
Here's a link we often refer new members to...
A better way to get help in the YJ Tech Forum
Originally posted in the General Discussion Forum by NonRubicon in May 2014. It's every bit as relevant today as it was then. ....................................................................................................... I think there are a few things members here can do to help...
www.wranglerforum.com
Good Luck, L.M.
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