1999 f250 speedo not working o/d light flashing please help

[aariz82]

Couple of days ago i started the truck and when i started to drive the speedo was not working and when it shifted into 2 or 3rd the o/d light started to flash it shifts smooth. So did alot of research and people said to change the abs/vss on the diff so i did that nothing happened. Do you guys think i should change the oss which is 50 bucks from ford part# F81Z-7M101-AA. Also 2 days ago randomly the speedo worked and o/d light stopped flashing and i thought everything was fine then it happened again. I need some help guys.

[7.34ever]

an intermediate problem like this could be tough to diagnose as you may know. not sure it would throw a code but could hook er up to check. in the older trucks the flashing light was often a tc module problem. if you know someone else with a '99 you could swap the oss and see if it changes. also, just as a precaution check and clean all the plugs well to make sure.

on my old 99 at work the speedo would randomly not work and everything looked fine. i'd get goin down the hiway, slam er in neutral, shut the truck off, then restart it goin down the road and it would start workin. lol i only did that when it mattered like on I5. that one ended up bein the abs/vss on the diff. good luck man

[aariz82]

well not its constant with the speedo not working and o/d light flashing. I was wondering does the oss (output shaft sensor) on the transmission have anything to do with the speedo not working? I am so tired of this problem. I had the transmission replaced last year and a good friends transmission shop all new parts. So thats why i think its electrical problem. If the o/d light is flashing can i run a scanner on it to get a code?

[7.34ever]

that's what i meant about getting a code. i'm not sure it'd throw one at ya or not but worth a try. i'd try to swap the oss with someone elses if you can to see if it changes the results before spending money on the part yourself. gotta hit the hay brotha, good luck again

[aariz82]

Thanks for the info buddy I will try tomorrow at autozone to get a code. I wish I knew someone else with a 7.3 like mine so I could swap the oss, I would really hate to buy it and it not fix my problem. I feel so stumped. Anyone else have any ideas?

[aariz82]

Is there anyway to check the oss with a volt meter to see if its bad, if so what should it read?

[aariz82]

i checked the wiring harness coming off the vss with a voltmeter and got a reading of 4.9v is that what its suppose to be?

[7.34ever]

come on guys. someone with more knowledge of this needs to help out our brother stroker addict

[aariz82]

Please really need info on this!!

[7.34ever]

c'mon wrenchers give the brother an idea