abs/vss/p0500 help!! no speedo

[Black92Coupe]

so about 2 weeks ago i fired up my truck and went to go hook up the trailer, i noticed when i started moving that the ABS light came on, no big deal .then i noticed that the speedo wasnt moving then all of a sudden it dropped down below 0.
did some reading to come find out that its most likely the sensor in the rear diff, tryed to test it but it seemed dead so i just replaced it with a new one. after a couple miles everything fixed itself, speedo came back and abs light went off....


so today i fire up the truck, go to hook up the trailer(maybe its cursed lol) and the same BS happens, the abs light comes on, hit the road and the speedo needle goes below 0

is the same sensor dead again? what would cause this, anything wiring related i can check out? maybe the diffs tore up inside and toasting sensors? cheap/junky sensor just S#$% the bed maybe?

maybe its the sensor in the tranny this time? i get a p0500 code this time,didnt even think to check for coded with the edge last time.

any help would be appreciated!

gonna wait till tomorow to crawl underneath there and see if the sensor is dead again

[Mark Kovalsky]

It isn't any sensor on the transmission. It is either another bad sensor or a problem with the wiring between the sensor and the PCM.

[dieselmac]

Check the wires between the sensor and the main wire loom along the drivers side frame rail. I bet you have a chafed wire.

This circuit is VERY voltage sensitive. A nick in the insulation or even a mashed wire is enough to mess it up. You can get a new pigtail from Ford.

Be sure you solder the splice in or you'll be back in the same boat w/in a year or so.

[Black92Coupe]

I followed every inch of wire with no luck. Was really hoping id find a chafed wire so i would know a new sensor would do the job. Dont want to waste another 80 bucks. In the last day a mouse decided to make a home in my glove box and one behind my alternator. Couldnt see any wires damaged, are these areas even any where near the wire that runs from the sensor inside the cab?
Thanks for the help guys

[Mark Kovalsky]

Did you check the wiring visually or electrically? A visual check is next to useless.

[Black92Coupe]

Yes just visually. Would have to chafe through the loom to get to the wire. All loom is intact. I do have a powerprobe and short tracer that im getting back from my friend. Gonna run that along the harness tomorow but theres areas like behind the gas tank that were hard enough to get at to even have a look, that i wont be able to trace.
Thanks

[Black92Coupe]

I doubt this matters but the light comes on when i hit the brakes for the first time.

[Mark Kovalsky]

To check the wire electrically you don't need to see the whole harness, just each end.

What light comes on when you hit the brakes?

[Black92Coupe]

Abs light. I had access to the harness from front to back no problems in that part of the harness. Anythibf else i can try?

[FlappersFtoy]

You kinda lost me...does this happen with or with out the trailer hooked up?
or does it matter.
Mine was doing some thing very simlair this summer but only when I was hooked up to the trailer ..but not every time.
Turned out that my trailer axle chaffed the trailer brake wires and would fault out the trucks abs whenever it grounded. shut off the truck start it back up fault went away...but it would come back on randomly while toweing .

all fixed now.
good luck

[Mark Kovalsky]

Originally Posted by Black92Coupe

Abs light. I had access to the harness from front to back no problems in that part of the harness. Anythibf else i can try?

No, there is not. With what you are willing to do to fix the problem this truck is not repairable.

I've told you twice what you can do to find the problem and you won't do it, so this truck can't be repaired.

[Black92Coupe]

How did you say anything that helps. Obviously iy has to be checked electrically so some useful info as how to go about testing/repairing would help. It really pisses me off when people say i cant fix something so stop being discouraging. I really appreciate the help, but thats not helpful.

I disconnected both ends of the wire, jumped one end and tested the other side for resistance/ continuity. No problems from diff to front connector. Now what!?

Please give me these suggestions again as re-reading only gets me "test it electrically or your truck is not repairable.

Thanks

[Mark Kovalsky]

Now you finally started testing. I told you twice to check the harness electrically, and all you said was you looked at the harness, and some of it is hard to get to. You didn't say you tested it.

If you had asked how when I said to test it electrically I would have told you. Sometimes people get upset when I spell it out when they already know how. I have no way to tell what you know and what you don't know. All I could tell was that I twice suggested testing it electrically and you didn't say you did, but still asked what you could do.

You also need to check both wires from the diff to the PCM connector for shorts to ground and shorts to power. Just checking for continuity isn't enough.

[Paul H]

I have seen the wire break inside the insulation due to flex. The wire looked fine but when flexed it would not conduct.

any moisture that wicks back inside the insulation will cause the wire to corrode and not conduct up inside as well. Chased a problem like that on my 96 f350 drove me nuts but finally found it.

[Black92Coupe]

I think i might just buy a replacement plug and run the wires to the front myself and then solder onto the stock location, if i cant find anything with the short tracer
Thanks for the help guys!
For what its worth i bought a generic sensor not the oem ford part