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Discussion Starter #1
Hey guys i have an 03 f 350 6.0.. its a longbed with 4 doors..

My speedometer doesnt work, abs light is on, cruise doesnt work and odometer doesnt work... Now i know there a ton of info on this topic but let me tell you everything that i have tested so far..

I took it to a diesel mechanic and he was nice enough to scan it for me for free and he said i have the P0500 code.. But he told me the PCM is reading speed..( he actually showed me on his laptop a graph showing the speed all he did was put it in drive and let it roll 12 feet which was only generated 2mph)... Anyways so the PCM is reading speed.. I went ahead and replaced the VSS just to eliminate that.. I also did a guage sweep test just to make sure the spedo needle moves and it worked... So im at a loss right now.. if the PCM is reading speed i would say that i do not have any kind of short in the wires..( atleast from the VSS to the PCM and ABS control module).. I have checked all fuses.. The truck does have a aftermarket touch screen player in it that i did no put in so i dont know if there is a possibiltiy there? Someone told me that the windsheild wiper motor can cause the speedometer not to work but i have not tried disconnecting it yet.. PLEASE HELP ME???
 

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Old Fart
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I was going to ask if you changed the speed sensor, but the PCM reading speed tells me it works. I don't have an answer. Someone will.
 

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Curmudgeon
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Going 12 feet / 2 mph is not really a test I would sign off on that everything is good. It's been some time but I remember the speed signal going to the ABS first, then distributed to the other electronics of the truck. If there is any inconsistency off the VSS you can have issues.

While it was replaced, is the VSS a Motorcraft or other vendor part? Some aftermarket are actually the same part as Motorcraft, some are not and do not have the same resolution. It also would not hurt to pull the VSS and make sure it was not quickly contaminated by excessive iron particles in the rear axle lubricant. It will be fuzzy if it is. Anytime I have replaced a VSS I also have replaced the lubricant.

I would also closely check the wire harness between the frame and the VSS as some have experienced a broken wire from movement fatigue.

The best method for checking the signal is to look all the sensors from stopped to 50 mph. An oscilloscope graph view is best but depending on the type of test instrumentation a numeric value that has a high variability at moderate to higher speeds diagnosises a problem.
 
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From your fire wall to your dash there are data wires from your ecm to your dash module, I found once the guy who installed a stereo pulled on the wires and pulled one loose after a bit vibration did the rest lost the signal still had power sweep worked and with scan tool could watch everything work found the wire pulled loose from the crimp. Hope this helps.
 

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Senior Member
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If it's a 4wd truck and you have a bad front wheel bearing it can cause the abs speed sensor to malfunction. Jack the front end up off the ground and do a wiggle test on front wheels with one hand on top off wheel and one on bottom wiggling in-out from truck.

Harry
 
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