PCM Fuse- PLEASE HELP ASAP
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Junior User
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PCM Fuse- PLEASE HELP ASAP
Ok, I have an 01 X with a 7.3. Yesterday morning my wife ran to the store and it just died unexpectedly on the way there. It cranks fine but doens't display the WTS and doesn't apear to be getting fuel. I checked the fuel pump and it's not getting any power so I started checking fuses and found the 20a PCM Power fuse under the hood was blown (one of the big fueses, not the little blade). I tried changing the fuse but as soon as I turned the key to on it blew the new fuse. I read through the forums and found many posts refering to the fuel heater element so I disconected that, replaced the fuse again, but once again when I turned it on the fuse blew. This is my only transportation right now and I can't afford to take it in so any suggestions would be GREATLY appreciated. Thanks.
xTraveler
xTraveler
Tuned
Joined: Jul 2007
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From: So. Cal.
Hi. I hope someone can tell you what usuallly causes this. If you came to my shop with this the first thing I'd do would be to get out the wiring diagram and see what all that fuse feeds and look at the wiring to those feeds closely to find the short that's blowing the fuse.
Don't do this but when I was a kid we did what we called the smoke test. We'd bypass the fuse and watch closely to see where the smoke came from. That's where the short would be found. That test today could cost you thousands of dollars repairing the damage from the test and the towing bill on top of that.
Dave.
Don't do this but when I was a kid we did what we called the smoke test. We'd bypass the fuse and watch closely to see where the smoke came from. That's where the short would be found. That test today could cost you thousands of dollars repairing the damage from the test and the towing bill on top of that.
Dave.
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I'm desperate enough that I actually considered bypassing the fuse but then I read all the warnings about the sensitivity of the pcm and thought sending it a surge could be a very bad idea. Since I've already blow every 20a maxifuse the local parts store had I tried swapping a 30a fuse that controls something to do with towing but unfortunately it blew that just as quickly. I put a multimeter on there to see how many amps I'm really dealing with and it blew the fuse in the multimeter... I've asked everyone I know and they all assure me that a bad pcm won't blow the 20a fuse so I'm at a loss. I've tried searching online to figure out what else could be on the fuse but haven't had any luck so now I have a friend going through the wiring diagrams. Once again, I could really use some ideas.
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Thanks for the suggestions. When you said you're truck did it last weak was it the same problem blowing the PCM fuse? I think I found the BIG plug you're talking about but no corrosion and cleaning didn't solve my problem. Any other ideas PLEASE?
Senior User
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I had all the same symptoms that you have. After getting to about the point you're at, I had to give up and bring it into the dealer.
It turned out to be the IDM, or at least that's what they tell me it was. I bet them at 9am a case of beer that they couldn't have the truck fixed and back to me that day, and they won the bet.
It turned out to be the IDM, or at least that's what they tell me it was. I bet them at 9am a case of beer that they couldn't have the truck fixed and back to me that day, and they won the bet.
Tuned
Joined: Jul 2007
Posts: 289
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From: So. Cal.
Hi. If you have access to the wiring diagrams that's the way to go. Just follow every circuit that that fuse feeds and look for a short to ground. Maybe it even feeds some things you can unplug and eliminate the possibility that that unit is shorted inside. Don't keep using fuses though that could cost lots. Use the amp meter across the fuse terminals in the box and a helper to turn the key. If the amp meter shoots all the way up on the 10 amp scale, quickly disconect and try some other possible short. You may set some codes in the computer but if you find the problem and fix it the codes will go away after a while.
Dave.
Dave.
