Well I don't know too much about wiring and such so I'm going to need some major help with this one.

To make a long story short, occassionally when I come to a complete stop, the #23 fuse in my power distrubution box blows. This fuse powers the transmission and O2 sensors. It seems to happen pretty randomly. For instance, I drove over 100 miles in the city yesterday and it didn't blow until some kid fell off his bike in front of me and I had to slam on the brakes to keep from hitting him. Aside from yesterday, though, it seems to happen roughly every 40 miles and during normal deceleration. My thoughts are that there is a wire somewhere that has worn through the insulation and when I come to a stop it gets pinched and shorts the circuit. I guess it could also be a problem within the transmission but I'm really hoping it's not. When the fuse blows, the truck goes into limp mode and the OD light starts flashing. I replace the fuse and it's fine again. Any thoughts?

Oh, sorry... It's a 2002 4.6l auto 83K miles.

 

A common cause of this is melted O2 wiring harness. You need to check through all 4 of them first. Seems to make sense, when you hit a large bump or come to an abrupt stop, the chaffed / melted harness hits the exhst pipe, and short to ground, fuse blows.

That is a first guess on my part. There are other things, but this seems to be at the top of the list for problem resoultions ( for those who post back the resoultion ).

 

That was pretty much my first thought. I checked them all as well as I could while laying under my truck on the driveway. I'll have to get it up on a rack to get a better look.

 

Did you check all 4 of them ? There are 2 by the pre cats, and 2 after the last set of cats.

This might not be the soultion to your problem, this is jsut the most common one reported back, from those who post a solution

When checking, the chaffed harness is usually between the O2 sensor and the connector for it.

IF you run your hand all the way around the harness and it is good, we will have to look at the list of items also connected to this circuit next.

 

I checked all 4 of them the best I could without having the truck on a lift. I did notice that one of them was hitting the transfer case linkage and was worn down a bit but I don't think the wire was exposed. All the mudding I've done is finally coming back to haunt me because everything under there is now the same color (brown) and crap falls in my eyes every time I touch something. I'm probably going to take it to a friend's shop tomorrow and have him put it up on a rack and just look it over. I'll post whatever I find.

 

Now you know why JMC runs a sprinkler under his truck after he goes off roading.

 

Yeah I try to wash as much off as possible but it gets into every nook and cranny and I just don't feel like laying under the truck with a hose for two hours every time I go off road. I guess a sprinkler would work, but with my luck I'd fall asleep and run up the water bill lol. What makes it even worse is the fact that I don't have wheel well cover things in the back and the ones in the front stop about 3 inches short of where they should so when I have all 4 tires flinging mud, it becomes a big mess.

I wasn't able to get to the shop today and I probably won't be able to until Monday but like I said I'll post whatever I do/don't find.

 

Alright I traced the o2 sensor wires up to the harnesses and everything looks okay. Where do I go from here?

 

Well I fixed the problem and thought I'd post it in case anybody else has the same issue. I took the steering wheel off and there were a couple wires going into the shift lever (for the OD). They had wore through the insulation from contact with some other part in there (sorry, I can't remember what it was). A little silicone and electrical tape and it's fixed. I spoke to a guy who said that he had seen two other trucks with the same problem so I guess it's somewhat common.