96 Mustang GT coil pack signal wire shorted to ground - Ford Mustang Forums : Corral.net Mustang Forum
 
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post #1 of 8 Old 04-27-2016, 07:44 PM Thread Starter
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96 Mustang GT coil pack signal wire shorted to ground

Have a no start issue with my 96 Mustang GT. Found out that if I disconnected the power/signal plug on the drivers side coil pack engine starts obviously running poorly on 4 cylinders. The pink/wht signal wire is showing a dead short to ground which i'm sure is causing the problem. The problem is I cant find where the wire physically goes. I know it connects to the pcm but not sure what route it takes to get there. I can't find a plug diagram with pinouts. Any help would be appreciated.

Thanks,
JR

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post #2 of 8 Old 04-28-2016, 12:27 AM
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a shorted signal wire will take out 1 coil pack, not both, therefore it should run on 6

look at places with heat and vibration along the harness


89 GT gr-40, KB2200(10psi), tweecer R/T,LC-1, 22gal cell, w/tailpipes.
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post #3 of 8 Old 04-28-2016, 01:55 AM Thread Starter
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I meant 4 because only the passenger side coil pack is connected. I'm pretty sure the PCM is bad though. Once I unplug the PCM the short disappears. Plug it back in shorts there again.
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JR
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post #4 of 8 Old 04-28-2016, 09:34 AM
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take the ecm,

reconnect the battery

use a test light to battery positive, and touch both control wires to that pack, does it light?

your diag of unplugging the ground, has NOT shown that it is the problem, there is wire in between that you need to check

89 GT gr-40, KB2200(10psi), tweecer R/T,LC-1, 22gal cell, w/tailpipes.
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post #5 of 8 Old 04-28-2016, 04:19 PM Thread Starter
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The signal wire goes straight to the pcm. When I disconnect the plug at the pcm the short is no longer there. A short in the wire before the pcm would still show regardless of the pcm being plugged in or not. This leads me to believe the pcm has an internal short. The other 3 signal wires have no continuity to ground. I would love to be wrong but it seems pretty straightforward.
JR
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post #6 of 8 Old 04-28-2016, 05:37 PM Thread Starter
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Quote:
Originally Posted by indy2000 View Post
take the ecm,

reconnect the battery

use a test light to battery positive, and touch both control wires to that pack, does it light?

your diag of unplugging the ground, has NOT shown that it is the problem, there is wire in between that you need to check
I tried this and as I expected, the light came on when I touched the pink/wht shorted control wire. Pulled the pcm plug and no light.

JR
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post #7 of 8 Old 04-28-2016, 06:04 PM Thread Starter
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The pink/wht control wire goes to pin 78 at the pcm connector. I confirmed continuity between pin 78 on the pcm plug and the pink/wht wire at the connector on the coil pack. There is no continuity between pin 78 and ground. I'm certain there is no short in the wire. Time to order a PCM.

Thanks,
Jenaro
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post #8 of 8 Old 04-28-2016, 08:31 PM
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I would not rely on a ohm check./

use a test light,,,,,,,you need current

89 GT gr-40, KB2200(10psi), tweecer R/T,LC-1, 22gal cell, w/tailpipes.
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