PDC relays SKIM fuse keeps blowing

Schwifty Rich

Schwifty Rich

TJ Enthusiast
Joined
Apr 21, 2018
Messages
226
Location
St. Louis, MO, USA
Hey everyone,

So I was heading out for my first off road outing and the jeep drove without any issue for about an hour and a half. While I’m going down the hill to the entrance of the park the engine dies and I have to pull over.

Symptoms=
No gauges worked
Fuel light came on with a full tank
CEL came on after leaving the key on acc for about a min
No ASD relay click
No fuel pump whirr

When we realized the ASD and the fuel pump were not coming on and switched the horn relay with them to see if we could get it to click, no luck. Out of ideas and lacking cell reception we gave up for the time being. I hopped in my buddy’s jeep and went wheeling with him while we left mine in the field of the 4x4 park. We ended up trailering it back home so we could really look at it in the morning.

After intensive googling we replaced the Crankshaft Position Sensor as others experiencing these symptoms had done but that didn’t help. We check for spark and did a bench test on the coil packs which were good. We replaced the PCM with another Tj and that didn’t help. We were about ready to drop the fuel tank and check the pump when we realized we had somehow we missed checking the fuse box behind the glove box. It turned out that the 10a PDC relays Skim fuse had blown. So we replaced it and tada the jeep was alive again! I ran to the gas station a couple miles down the road and on the way back it dies again going downhill. The same fuse had blown again so I popped it out replaced it and started going again. As I’m pulling in the drive way downhill it dies again. Ok so there is some kind of short is what I’m thinking. I wanted to see if I could just make it back to my house so I stocked up on fuses and attempted to back out of the driveway and I probably went through 4 fuses before I gave up that hope.
So I left it at my buddies and I’m headed over this weekend so we can really dig into it.

I’m looking for any help or direction regarding what could be causing the short or where to look. Can I get a new section of harness for that and just replace it and be done with it or would I need to buy the whole $400 harness kit?

I really want to hit the ground running, come with ideas, parts, and a better understanding so that it doesn’t sit for another week.

pdc diagram.PNG
 
I'm horrible with electronic stuff like this, but he brings up a good point about the fuel pump relay being a potential culprit.
 
I had a leaking fuel line replaced, which required dropping the gas tank. A few days later I was wheeling, and the fuel pump electrical connector near the tank came loose because the locking tab had broken off. I reconnected and continued the ride. Next time out I started blowing fuel pump fuses and suspected a short in the pigtail around the tank. Took it back to the shop. They dropped the tank again and found the wire insulation worn through, allowing the conductor to short against the tank. I had to pull on the pigtail to reconnect the junction, and it must have pulled the wire in a tight spot where it wore through. They also cable-tied the connector together so it won't come apart again.

Good luck with your search.


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Since I have to wait till the weekend to work on it I've been googling to the best of my ability and taking in what you have suggested.
I'll replace the fuse, and switch the horn relay for the fuel pump relay and see how that goes. Next I'll check the 02 sensor wiring because I've read that can easily get hot and cause shorts there too. Last I'll drop the fuel tank and check the connectors there.
I'm always open to more suggestions and help so thank you guys for the info so far!
 
OK, quick update. My buddies Dad decided to test it out during the week. After it had been sitting for a few days he popped a new fuse into the PDC relay #12 in the glove box and off he went. He said it drove fine all day long but it died suddenly for no reason it seemed. He went through 3 fuses just getting it back home and when it was back home it was the same story. Every time the key is turned the engine starts up no issue but you try to release the clutch to go anywhere and Fuse #12 pops! What could that mean?

Fairly sure its not a relay issue as it all functions correctly at startup and turns over fine. He checked to 02 sensor wires as when he was poking around and they looked fine too. It seems to be temperature related but I cant think what could be causing the fuse to pop.

We are going to trace the wires back and see what we find but does anyone have any other ideas just in case? Are there any resources that show the ground wire locations by chance so we can make sure to check all of them?
 
Searching the FSM I was able to discover a list and pictures of the connector and ground locations!
Just an FYI the page identifier is 8W - 91 for my 2003 Manual.
 
So we found what we believe to be the short. Checked continuity to the fuse in the glove box successfully and when we ground it to the battery it blew the same fuse. Turns out the wire was rubbing against some jagged metal from my fenders. Wore right through the plastic wire surround. Cut it and put a connector on it and got some old heater hose and wrapped it around the problem area for preventative measures. Let's hope that short was it! Ready to go wheeling today!
 
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