Hi guys,
last week I bought a 97 F150 4x4 with the 4.6 seems like a decent truck. The other day the overdrive off light started flashing at highway speeds. The truck still shifts fine I have seen no issues with the speedometer. Just to be safe I had it ran on a snap on reader and got the PO503 error code. I cleaned the speed sensor it looked good, but still the same thing. Since the sensor was only $20 I just bought a new one and still the same thing. Fuses all checked good. I wouldn't think it would be the PCM since it starts and drives fine but I just don't know. Where would you guys look next. I checked all the wiring it looked good nothing was hanging down near the exhaust. Once you shut the truck off and restart it, the light is off, it will stay off at low gear speeds, and only comes on after 2-4 miles of highway speeds.
Thanks Guys,
Jennifer

 

P0503 Vehicle Speed Sensor (VSS) A Intermittent/Erratic/High


Probe the wires while it jacked up running and in gear.

Check power VRef @ the connector

or try another.

 

I'd get it elsewhere.

 

I ran by and got my truck put back on the reader the PO503 error is fixed but a new code came up P1500, so I went home and took the input/output sensor out and cleaned it really good, it was pretty filthy put it back in and ran back and got it scanned again the light was still flashing but said no codes found. Reset the computer and drove 2 drive cycles and the light finally stopped and I drove several hours today and it is still off so looks like I was pretty lucky $50 for the initial reading and he said he would read it until I got it fixed(he was pretty cool about that) and $20 for the VSS. I am still don't understand that the P1500 code didn't come up the first time it only showed after i got the PO503 issue resolved either way I lucked out on the problem.

only problem I have now, is the door ajar light plus dome light and dinger won't shut off not exactly sure why, but it started the minute I fixed everything else LOL go figure