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99 F-450 O/D light flashing

Discussion in 'Ford Trucks' started by jkiser96, Dec 1, 2010.

  1. jkiser96

    jkiser96 Senior Member
    Messages: 401

    I have been having issues with my trucks speedo not working intermittenly. It started it again this morning & now the O'D light flashes when I put it in reverse or park but not while in drive. I have been told that I may have a tooth off the speedo gear & it depends on where that gear is when I park it as to whne it acts up. Anyone else had this issue? Just checking to see what is out there.
  2. damian

    damian Senior Member
    Messages: 330

    replace the speed sensor located on the top of the rear end housing,also check the harness that goes to it,we see problems with them,ford sell a harness repair kit to fix it. as you know,the flashing od light is the check engine light for the transmission,you need to scan the ecm,retrieve codes and diag those.
  3. mrv8outboard

    mrv8outboard Senior Member
    Messages: 197

    Do you have other lights on on the dash? ABS light? I had a similar issue early October, During a tow home from the drag strip my ABS light came on, then after awhile my OD light was flashing. Once home I put it on my scan tool and found codes for the speed sensor and one the basically said the trans was slipping and needed rebuilding. Knowing that I had no previous tranny problems I addressed the ABS sensor (vehicle speed sensor) first. That was it. It is also were the PCM receives 3rd gear output info, so if the sensor or circuitry is faulty it thinks the transmission is slipping. Put it on a scan tool, retrieve the codes, R+R the sensor.