Question about 2002 Ford Mustang

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2002 Mustang blowing PCM fuses

My 2002 Saleen quit running the other day, and it is blowing 30A PCM fuses like it has a short to ground. So far I have traced it to the white/blue wire that runs from a gray connector by the ECM R/S kickpanel, it runs in the harness behind the dash/radio etc.... and runs to the driver's ignition area, I think it is a PATS receiver or something like that. If I remove that wire from the connector by the ECM, the fuse doesnt blow, but as soon as I touch it POP. Also, if the relay module in the R/F fender is unplugged, it wont blow. Also, its a supercharged S281, so I discinnected all the Saleen intercooler wiring into the relay module to eliminate their electronics. Anyone have any clue whats going on? I cant find that wire shorting anywhere, its inside a big thick harness and I dont wanna take the whole thing apart and trace it, I guess it could be rubbing a ground wire in the harness somehow. It shows it goes to ground through the ohm meter, it also shows the wire has continuity from end to end, so its not broken. I am using Alldata to see the diagram, but it is ridiculous and terribly inaccurate. I am at my wits end.

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  • Peter Castaldo
    Peter Castaldo Feb 11, 2009

    With all due respect Im a Master technician and this is the short version of the 4 hours I spent diagnosing this today. Im a Toyota dealership technician, so Im used to having the best manuals and computer diagrams at hand and Ford cars are a little different (I have 4). The problem is I dont know what else runs off this wire, it appears it doesnt go anywhere else other than straight across, and Alldata is worthless for this diagram. There is either a shirt in the wire or a bad CCRM, which isnt uncommon. I think Im gonna try a CCRM

  • Peter Castaldo
    Peter Castaldo Feb 11, 2009

    chuck943 Thank you very much, makes alot of sense now, I felt like I was working in circles. I know the engine and its wiring like the back of my hand and Ive looked at everything 3 times, and I dont see anything pinched at all. I saw the coil packs in the diagram but the colors it was saying didnt make sense so I didnt look any further into them, but I will certainly start looking in a couple new directions tomorrow. Ive been using a circuit breaker in place of the fuse, so its pretty easy to tell when I have or havent fixed it. I had that square connector unplugged, and the fuse wouldnt blow, so that was telling me the problem was inside the car, but now that I know thats the coil side, I see a little more clearly now. Thanks again, I'll let you know what I find, let me know if you think of anything else.

  • Peter Castaldo
    Peter Castaldo Feb 11, 2009

    OK, well the car is fixed. Today I focused under the hood and found a wire harness touching the EGR pipe and causing a red wire to short out. Thanks for the help!

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  • Ford Master
  • 783 Answers

Ok the 30 amp fuse is the switch side of the PCM relay and the W/BL wire u are disconnecting is the coil side of the relay.So when u disconnect it u are keeping the relay from energizing so this is not the problem.When u unplug the CCRM in the fender u also keep the relay from energizing.
Unfortunatley this could be the worst possible ckt to have a short on because it feeds everything with a 12V feed in the emission system.
It feeds all the coil packs,the coil side of the low and high speed fan relays and coil side of AC relay also in the CCRM.
Now looking at the schematic I think it is possible to narrow your problem down to the coil packs.The other ckts off of this go thru 2 more fuses, fuse 8 and 2 in the interior fuse panel and both of these are 20 amp fuses so they should blow before the 30 amp if the short was after them. Although it could be the CCRM I doubt it would blow the 30 amp fuse because the other feeds there are on the coil side of the relays so that leaves the coil packs.
I would trace the red wire side of each coil pack looking for a pinched wire,they will go back to right side of engine into a square 42 pin connecter.A quick way to test it is to unhook all the coil packs then get you 2 alligator clip wires and a 1157 bulb like in your t/signals. Clip one of the wires on each side of the bulb and hook one wire to power then the other to the red wire pin 24 of the CCRM that u unhooked in the fender(leave CCRM unhooked). Pull the 2 fuses in the interior fuse panel (8&2) then see if your bulb lights. If it does then u have a short in the wiring,if it doesn't then hook each coil pack back up one at a time and see if it lights your bulb.

Posted on Feb 11, 2009

  • Chuck Martin
    Chuck Martin Feb 11, 2009

    Good! Glad to hear u yamed the beast.

  • Chuck Martin
    Chuck Martin Feb 11, 2009

    Sorry, Tamed the beast

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  • Master
  • 1,596 Answers

With all due RESPECT to You Are NOT AT WITS end Most People Don't Know To Take the first step You Did Electrical Can Make you Think you Are at Wits End That's All You Got this<<<
The Wire That Shows Continuity and Blows the Fuse & what Component it Controls are the Problem YES Open The Harness There Could Be A Potentual FIRE in there Open it to Be sure it has not Damaged any other Wires and or anything Hasnt Damaged IT ALSO. This Does Not end here so Don't Rate Me Unless You Find this Truely Helpfull Let Me Know You FIND
ANY MODIFICATION TO STOCK WIRING HAS THE POTENTUAL TO DESTROY A VEHICLE IF IT IS NOT DONE CORRECTLY SO BE SUSPICIOUS OF ADDONS Rate Me As Fair As You Feel. Good luck

Posted on Feb 11, 2009

  • Ronnie Wilson Feb 11, 2009

    I Am Also A Master Thec of 30 Years And ASE's Blessings

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