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Unread 07-11-2014, 06:43 PM   #1
jish
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Grounded PDC from ignition switch

My WJ was running rough and threw a code for open circuit fuel injector. Replaced the injector, chased back wiring to PDC to find out the injector and circuitry was fine, but when my ignition is switched to ON, the PDC is grounded and only 24ohm resistance to the main ground at battery. Replaced ignition switch, that wasn't the problem either. Two wires at the ignition switch are sort of grounded, blue wire has 40ohms resistance, and red/black has ~60ohms resistance to main ground.
Anyone ever seen this, or more importantly, does anyone know what those two wires go to? Really don't want to take the dashboard out.
Cheers
- Josh

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Unread 07-12-2014, 03:31 PM   #2
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Unread 07-15-2014, 11:57 AM   #3
jish
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Bumppp
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Unread 07-15-2014, 06:12 PM   #4
rm2001wj
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Please don't be offended, but your description of what's happening is very confusing. Your refer to PDC (that is actually the Power Distribution Center), when probably you mean the PCM (Powertrain Control Module. You also say it is grounded, but then say there is 24 ohms resistance to the battery ground. When something is grounded, then the resistance between it and the battery ground essentially zero.

At any rate, you are not likely to get any meaningful responses until your problems are more clearly stated.
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Unread 07-15-2014, 09:12 PM   #5
jish
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Quote:
Originally Posted by rm2001wj View Post
Please don't be offended, but your description of what's happening is very confusing. Your refer to PDC (that is actually the Power Distribution Center), when probably you mean the PCM (Powertrain Control Module. You also say it is grounded, but then say there is 24 ohms resistance to the battery ground. When something is grounded, then the resistance between it and the battery ground essentially zero.

At any rate, you are not likely to get any meaningful responses until your problems are more clearly stated.
I am not offended. However, when I say PDC, I do in fact mean the Power Distribution Center. When I say grounded, I mean that when I use a multimeter to perform a continuity beep test, it comes back positive for continuity between the negative side of the battery and the PDC power board.
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Unread 07-15-2014, 09:34 PM   #6
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The code says you have an open circuit at injector. I'm not sure what the PCM has anything to do with it, even less the ignition switch. You need to check the wiring between that particular injector and the ECM.
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Unread 07-15-2014, 09:44 PM   #7
jish
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The injector circuit wiring is fine between the PCM and the injectors. As well, the shared power to the injector circuit
from the PDC is fine. The ignition switch comes into play because the PDC gets grounded from the red wire that runs to the ignition switch from the ignition fuse on the PDC, and is getting grounded from the blue or red/black wire that also goes to ignition switch.
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Unread 07-15-2014, 10:08 PM   #8
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How exactly did you determine the wiring between PCM and injector was fine?
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Unread 07-15-2014, 10:26 PM   #9
jish
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Physically took the loom apart and followed the wire back to the PCM. Also put the multimeter on it showing 0 resistence from the PCM to the injector plug. The PCM being plugged in or not has no correlation to the grounded PDC board. The problem is not at all the injector circuit.

At this point I am just going to remove the dash and keep chasing the two suspect wires that are grounding out my PDC.
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Unread 07-15-2014, 10:50 PM   #10
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There are two wires going to the injector. The PCM provides a signal and a ground. Did you test both?
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Unread 07-15-2014, 10:57 PM   #11
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And what resistance values are you getting with 3 decimals digits?
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Unread 07-19-2014, 03:15 PM   #12
jish
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I think I may have found the issue. Pulled the BCM (body control module), as this is where my two suspect semi-grounded wires from ignition switch were leading. Once pulled, I no longer have sudo continuity between the two battery terminals. For those who don't understand, the ground was finding it's way to the PDC through the ignition and jumping through the Injector circuit being it was the path of least resistence.
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Last edited by jish; 07-20-2014 at 02:18 PM..
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Unread 07-19-2014, 03:22 PM   #13
rdkendrick
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Very strange problem. Good thing you are persistent. I would have given up.

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Unread 07-20-2014, 02:17 PM   #14
jish
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Welp, seems my WJ is a heap of electrical awesomeness. BCM was not the issue. When I pull fuses 21 & 22 out of the interior fuse box the two battery terminals no longer have continuity. Fuse 21 is Ignition Run/Start - PDC and fuse 22 is Ignition Run/Start. I suppose I need a wiring diagram for these two wires still, find where they go, and just start ripping everything apart that these two wires touch. Any suggestions on a FSM or wiring diagram?
Thanks
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Unread 07-20-2014, 10:47 PM   #15
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Quote:
Originally Posted by jish View Post
Also put the multimeter on it showing 0 resistence.
Let's try this again. 0 point what is your resistance? 18 AWG wire running 3-4 feet from the computer to the injector will have a normal resistance of about .02 ohm (there has to be SOME resistance). If resistance is higher, even slightly, the computer might interpret it as an open circuit. If you run your multi-meter on continuity test mode and are getting a 0.000, you are using the wrong setting. You need the lowest setting on ohmmeter mode, with decimals.

What is the code it's throwing by the way?
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