So I've had my truck back to the tranny shop to get a code pulled for a flashing o/d light, and it pulls P0503 again. The first time they said the speed sensor was bad, so I put a new one in a few weeks ago. They said the speed sensor was bad again this time, so I pulled the new one out and got it replaced at autozone with a brand new one yesterday. It threw the code again today after driving about 30 miles.

The truck seems to shift ok, but it works pretty hard to climb hills. Anyone have any ideas?




'98 f150 4x4 automatic 4.6

 

Have you checked the connector? Check the wiring to the connector, pull the ribbed covering open at look at the wiring as far back as you can. Look for rubs on the harness.

 

The code says noisey signal. It's not the sensor, now.
Harness???? Connector???

 

will do this weekend. thxs

 

I just had a crazy idea. THe speed sensor the tranny shop showed me goes into the transfer case. I see on alldatadiy that there is an output shaft speed sensor on the tranny.

Maybe I have been messing with the wrong one?

 

I finally figured this out. As long as I keep my fuel tank at least 3/4 full, the light stays off.
Strange.

 

I had a similar problem, the dealer detected RFI on the circuit, and traced it back to the gas pump, when the induction pump starts getting old or dirty, the piston works harder; thus, causing electomagnetic interference on the wires, which by the way, run along side the pump wires and the trailer towing harness. If the problem continues, take it to the dealer, they know how to detect RFI affecting the wiring harness.

 

Use an old pocket radio ( transistor) If there is RFI it will pick it up as static , the closer to the source the more static you will get , Its old school but it works.

 

You could also use an inductive mic such as a tone generator set.

Try cleaning the grounds for the fuel pump. That might help with it.