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Hello Im new to this form, I have read many posts to try and figure out what the problem is with my F-350 6.0. I have an intermittent problem with my Speedo reading zero while I'm doing 70mph on the fwy. since the speedo won't work the truck goes into limp mode, the turbo will not function at optimum level. I have replaced the diff. sensor, the trani sensor, the a.b.s.sensors, the instrument cluster to a reman cluster. Then when I had a local mechanic plug a laptop dianostic program on it as he was running through the system inadvertently the radio cut out, so I found that who ever installed the after market stereo they cut a few wires to the harness, I went to the junk yard found the harness end and replaced the end. so with all that said and done no one knows what is causing this speedo not to work and limp mode. about 4 years ago the oil pump stopped working and ruined the turbo so the whole front end of that glorious 6.0 was rebuilt the problem started about a year after that. Any suggestions????
Well limp mode comes from the TPS throttle position in the EGR valve any codes popping up recently ? Try cleaning the valve and monitor EGR vp valve position,EGR desired , EGR dc duty cycle , I think there's more than one issue your chasing .
Last edited by 04badford; Oct 15, 2016 at 07:16 PM.
Reason: Adding