F150 '04 triton XLT (not heritage) 4x4
165000 miles

Current symptoms:
OD Light flashing, at turn on, in park and at complete stop, along with driving at any speed
ABS light - solid
OD jumps in and out, usually accompanied by the flashing light
After the battery is unplugged it runs perfectly for about 20 miles (no OD flash but ABS light is still constant)

What I've done:
Replaced Trans
Installed aftermarket radio and subwoofer
Replaced battery
Replaced TRS
Checked Tcase fluid (clean and full)
Checked Trans & engine and radiator fluid
Inspected the inside of computer visually (no smell, no burns, looks fine)

What I've narrowed my possible issues down to:
Mystery chaffed wire (that Trans guy didn't find)
Computer (despite its perfect appearance)
Transmission speed sensor/Speed sensor located on differential (yet I've never thrown a code for it and have no speedo issues)

I'm completely at a loss. If you have any advice or experience please help! I've poured a lot of time, research and money into this Ford so far.

Thanks for reading!

Back story -

Bought this truck from a dealer. Ran fine on test drive, despite solid ABS light, but was a total wreck by the time we got it home. A few weeks later, after checking things out, we decided to replace the Trans. Took it to a local shop that we had (limited) experience with. When we picked it up it drove fine for nearly five months (we drove with a four wheeler in the bed, drove 60+ miles distance about once a week, plus regular grocery getting - but not a drive to work vehicle). Then we drove it for a 100 mile trip with a load, performed fine on the way there, and we parked it for a few hours. On the way home, the overdrive off light flashed for the first time since we replaced the Trans. We continued home and went to our Trans guy ASAP. The CEL threw a code for the TRS sensor. Trans guy replaced sensor and the CEL (still reading malfunction from TRS) and OD light continued. Trans guy said when the truck is off it checked out fine on his diagnostic computer and only once it was powered on did the TRS appear not to work. We left it with him to check for chaffed or broken wires. He didn't find anything, and came to the conclusion that it could be our computer.
This leaves me in a difficult situation - Its like I have to change the computer to prove to my Trans guy the Trans is the problem, if it is at all. This is an expensive transmission!

 

Why don't you get the codes read? With the code you'll know what's wrong. Without the codes all you can do is keep buying parts until you get lucky. This is nearly impossible to fix without knowing the codes that are stored.

 

thanks for the reply mark. The code it throws is for the TRS sensor, which has been changed since the code was read to no avail (which is why I'm getting the - "it must be your computer" from my Trans shop). I can't remember the abs code, but my Trans guy acknowledged it and didn't think it was a factor related to Trans or OD- rather it enforced his belief it was a computer issue vs. Trans issue. I was hoping someone with a similar problem could tell me they are very much related. I guess I'll have to find out for myself! Thanks again.

 

I don't think it's the computer. Computer failures are very rare.

There is no code that says to replace the TRS. If I knew what code I could help you, but without the codes all I can do is guess. My guess is that there is a problem with the wiring between the computer and the TRS. That will set the same code as a bad TRS.

If I knew what ABS code was set I might be able to help with that, too. But with what you have shard all I can say for sure is that something isn't right, and the computer is probably not the problem.

 

It prob has a chaffed harness at the back of the engine on the passenger side. The harness retainer gets broken and then the harness lays on the exhaust manifold and burns up. BTW, what is a TRS sensor? There is a TSS and a OSS. You prob have a bad diff sensor for the ABS concern, codes would be helpful.

 

TRS = Transmission Range Sensor. It is on the driver's side of the transmission where the shift cable attaches. It is the black plastic part with the wiring harness plugged in.

 

Wow I feel dumb, didnt even think of the range sensor lol. Anyways, thoroughly check the harness that runs behind the engine for chaffing or burning.