99-02 F250/350 7.3 diesel no comm

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  • BRIAN617
    Senior Member
    • Dec 2016
    • 153
    #1

    99-02 F250/350 7.3 diesel no comm

    Is there any real good info out there for these PCMs that have hit and miss communications?

    Causes, Fixes, Just bad PCMs?

    I've benched tested a few with test harness only built for power, grd and comm lines and get same results in vehicle.

    Sure makes it tough to diagnose actual engine problems.

    Also crazy to have to sell PCM just to diagnose other problems, when the PCM will still run the vehicle.
    Tags: None
    • diesel71
      Senior Member
      • Feb 2008
      • 932
      #2
      do you have more information?. any codes what issues are you getting?
      I usually see a p0605 or po603 code with a bad pcm. If the pcm had or has a physical chip plugged into the board at the rear then yes it will still run but have a biased pcm.

        Comment

        • BRIAN617
          Senior Member
          • Dec 2016
          • 153
          #3
          Originally posted by diesel71
          do you have more information?. any codes what issues are you getting?
          I usually see a p0605 or po603 code with a bad pcm. If the pcm had or has a physical chip plugged into the board at the rear then yes it will still run but have a biased pcm.
          This is just simply a communication problem with scanner(s)

          Two truck in the last three weeks. However I've also run into it before, seems to becoming more common.

          Current truck has valve cover harness problem, and I was able to finally get circuit codes cycling the key a few times to get comm.

          Truck before only communicated once or twice. It was a no start, but had crankcase full of fuel. Still I wanted to check IPC psi and % and only got one shot.

          Two different scanners OLD Modis and Verus Pro, same results.

          Bench testing them yields same results, so its not likely a rubbed wire under the right front seat crazy fix.

            Comment

            • Witsend
              Banned
              • Nov 2012
              • 2942
              #4
              Thought unplugging a water ingressed PRNDL switch or ABS module on some Fords would restore communication. Maybe worth a shot.

                Comment

                • BRIAN617
                  Senior Member
                  • Dec 2016
                  • 153
                  #5
                  Originally posted by Witsend
                  Thought unplugging a water ingressed PRNDL switch or ABS module on some Fords would restore communication. Maybe worth a shot.

                  Originally posted by BRIAN617
                  Bench testing them yields same results
                  I can eliminate any bad inputs to the PCM this way

                    Comment

                    • Witsend
                      Banned
                      • Nov 2012
                      • 2942
                      #6
                      I think I would hook up the battery charger and try my old MT2500 or an old Hickok NGS, crack open a few cold ones and try a Buzz test on myself

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