Recently the fuses for my transmission and OD switch started blowing. It happens when I just get on the gas from a complete stop or when I have to slam on the brakes. About 80% of the time it happens when the steering wheel is turned to the left. I spoke to some guy who said that his brother had the same problem. He said the wires to the OD button wear out from contact with some other component in the steering column. I took it apart and sure enough, the wires were bare. I fixed them up and went on my my way. All was good until a few hours later my truck just died. I checked all the fuses and found that the PCM fuse had blown. Replaced it and all was good... for about 10 more miles anyway, when the transmission fuse blew again. I took the steering column apart again today and could not find anything else out of the ordinary. It wasn't really a huge deal when it was just the tranny fuse because when it blew it would just go into limp mode and I could drive into a parking lot or something. With the PCM fuse, however, the truck just shuts off. Since it usually happens when I first take off from a light, I often get stranded in the middle of an intersection trying to replace a fuse. Any help would be appreciated.

 

You really need to add your truck's specifics to your profile. I can never remember what you drive.

 

What year is the truck and what fuse numbers are blowing and on which of 2 panels.
There are at least 3 fuses involving the PCM.
The OD lamp is on a 5 amp and powers more than just the OD lamp thru the ignition switch, on an 02 model year for example.

 

C'mon, Steve, with all the problems I post on here you still can't remember what I drive lol. It's an 02 4x4 4.6L Auto. The #29 fuse in the cab and the #23 fuse in the PDB are the ones that were originally blowing. #29 protects the Autolamp module (I have an XL, so I doubt I have this), OD control switch, central security module and Beltminder. #23 under the hood says HEGO sensor and automatic transmission.

The one that started blowing more recently is #2 in the PDB. It is labeled Powertrain Control Module.

 

Check your O2 sensor harness for melting on exhaust or chafing on drivetrain components.

Steve

 

I have already checked the o2 sensor harnesses thoroughly to no avail. I really thought I had solved the problem when I saw the bare wires in the steering column. Now I'm wondering if it's possible they are worn through in another location too.

 

The repair you made to the OD switch/light, where was this at ?

CJB Fuse #29 is fed through Connector C251, which if I recall correctly is at the base of the steering wheel column. Have you used the Tilt column lately or just started using it ? This is for the

CJB Fuse #29 also feeds :
CJB Fuse #29
Red w/ Yellow Stripe Circuit #640

Splice S225, then to ( still as Circuit 640 )
Trans Control switch ( what you alredy fixed ? ) - via C251
AutoLamp module ( which you said you don't have ) - via C216
CSM ( Central Security Module ) - via C256
Belt Minder Module - via C238

Don't know if you did any work under the seat any tiem lately ??

There are quite a few items for above, don't know if you have worked any of these or not.

BJB Fuse #23 is the circuit after the PCM Power Relay, which the power going into the N.O. contacts is BJB Fuse #2 - 30A.
At this point it is the Red w/ Yellow Stripe, Circuit 391.

After Splice S155, it changes to a Violet w/ White stripe, and the circuit is changed to 1138.

Splice S140 for the 2 connections to the Trans ( 4R100 with the 4x4 If I recall correctly ), remaining Circuit 1138, Violet w/ White stripe.
Circuit #1138 feeds ( internal to the Trans ) via pin #1 in Connector C193:
Coast Clutch Solenoid - Brown w/ Orange stripe pin 5 C193
Shift Solenoid B - Violet w/ Orange Stripe pin 2 C193
Tq Converter Clutch Solenoid - Violet w/ Yellow Stripe pin 4 C193
Shift Solenoid A - Orange w/ Yellow Stripe pin 3 C193

Also in Connector C193 on pin #12 is the Violet w/ White Stripe to the
Electronic Pressure Control Solenoid - White w/ Yellow Stripe pin 11

Each one of the Solenoids above exits the Trans via the same connector C193 to the PCM, via Connector C174. The Conector C193 pin and color assignments are listed above.

 

It looks like you spent a lot of time typing that so I hate to say that I have no idea what any of it means. To answer what I did understand, I do not have tilt wheel so that is out. The repair that I made was to the wires that go into the shift lever to the OD button. The wiring harness has a white connector on one end under the steering column. It goes up over the top of the steering column where it is held in by a couple plastic brackets, and then it goes up into the shift lever. I have found that those wires wearing down is not completely unheard of, as they wear from contact when shifting the transmission. The only work that I did before I started having these problems was rebuild the rearend and replace the alternator. I really try to stay away from electrical because I don't know much about it and find it's really easy to screw stuff up worse than it was. I posted this in hopes that somebody would have heard of the problem and know of an easy fix. If it's as complicated as your post made it sound, I'll probably just take it to an electrical shop when I can afford it. I appreciate your help.

 

I don't think it is complicated, but more so what might turn out to be an extended game of wheres waldo. Feel up for it, we can start at the top of the list with the OD switch, and take that from one end to the other, then move on to the next one on the list.

You up for this ? If so, I'm game, it is not like I have a nobel peace prize to work on or anything

 

I have a 1997 f150, Lariet. The 30 amp fuse(#24 in the power dist. box) for my PCM blows when accelerating from a stop. Of course the engine immed. dies. Replace the fuse and engine starts and runs fine. Maybe for only a few minutes, or maybe for 6 months. It always seems to occur when i get on the gas hard from a dead stop. The dealer did an electrical analysis and could not find the problem, said have it towed in when it occured again. Any suggestions?

 

See my post in

https://www.f150online.com/forums/sh...highlight=fuse

Steve

 

My thought would be that as the engine twists in it's mounts from torque, wires either cross or ground out.
You might move all harness around in all directions with the engine running to see if it happens.
It's possible that you may clearence the fault enough that it won't come back for some time, after doing this if not seen, so move them around in all directions an amount you judge they would move with engine twist.
Also look under for a burn on the exhaust.

 

Thank's guys for all the info. I moved the wiring harnesses under the hood and finally duplicated the fault. Traced it to a wire for the oxygen sensor after the catalitic conv. on rt side. A wire was rubbed bare and would touch a harness support as the engine was accelerated.
Again thanks, it took awhile to find the solution, but I was out of ideas until you gave me new leads.