speedometer not working
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speedometer not working
I have a 99 f-350 7.3l 6 speed manual. The speedometer and cruise does not work. I had an abs light on and changed the rear diff sensor, solved the abs light but the speedometer still does not work. Tried a different instrument panel with same results. I purchased this truck with this problem. I did a search on this forum and have been reading alot of different problems and all of them the speedometer tried to work or was intermintent. Mine does not work at all. From what I read it might be a pcm. one problem, what is a pcm and where is it located. Also can autozone check it or do I have to take it to a mechanic to be diagnosed. Another question I have, Is there anyway of disconnecting the speedometer that I could check and see if maybe the PO might have forgot to tell me,(fuze, wiring harness in the dash, ect.). Thanks for anyhelp
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Yes the speedometer and odometer are electronic. During the course of troubleshooting my problem I found out that the vss sensor on the rear diff sends a signal to the abs control module and the abs control module then interprets the signal and tells the speedometer and cruise control(throught the pcm) what to do. There is a gray wire with a black stripe going from the abs control module to the speedometer and pcm. In my case this wire was broke before the splice causing the symptoms you had. But since yours started working again after turning it off. I"m leaning toward the vss sensor or the abs control module.
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Post Fiend
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Clean the contacts of the sensors, and reset the computers, make sure the batteries are load tested good and alternator output is fine.
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my 1992 f-150 has the same problem when i got it the speedo did not work. replaced the vss or rear abs sensor and still have the problem any one know any thing about how to fix this i am driving from ohio to cali and woud like to solve this if possible
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