7.3 PCM(posted on the "other" site before I remembered im on this one)

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    7.3 PCM(posted on the "other" site before I remembered im on this one)

    I know its not the for sale section but figured Id get more traffic and people that actually had a clue. Got a shitty old 2001 f350 dump 7.3 auto and am 98% sure the pcm is fucked, so Im looking for a PMT2 code pcm if anyone has one.


    little back story: starts, runs, idles, and moves great. But has NO nuts, none whatsoever. Wont even spin the tires on dirt, boosted launch still no spinage(dont believe theres much if any boost). Unplug the MAP and it goes like a scalded rat, swap MAP with 2 different known good ones and still no nuts. Trucks the good MAP's came from both show about 14.06psia where as this dump truck shows 12.2psia, I'm about 1100' above sealevel so the 14.06 is about perfect. Unless I'm missing something?

    #2
    Do you have a way of seeing the PIDs? You should be able to hit 14-18PSI (gage, 28-32PSI absolute) in a stock truck at full tilt.

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      #3
      Originally posted by '84 Bronco II View Post
      Do you have a way of seeing the PIDs? You should be able to hit 14-18PSI (gage, 28-32PSI absolute) in a stock truck at full tilt.
      Used to use torque pro but all it does is freeze up now, downloaded a few others that seem to be decent. Its showing 12.2psia roughly all the time, brake boosting might go up a bit maybe to 13 nowhere near 28-32psia. I know the signal wire from the sensor to pin 79 on the PCM has like 1.7 ohms resistance which isnt terrible but checking a random 25' spool of wire its barely anything so that wire might be suspect, skewing the voltage the pcm sees.

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        #4
        Assuming the other trucks are Superduties and aren't manual transmissions, why not try one of the PCMs from those trucks? The hardware is the same to my knowledge regardless of PCM strategy. Sorry, I don't have a spare PCM for you to try, but I doubt it is the PCM anyways.

        Have you connected an independent pressure gauge to the MAP pressure line to verify that the MAP sensor is seeing actual manifold pressure? I'd suspect a boost leak on the MAP line causing the sensor to only see near ambient pressure and the PCM to not fuel as it should since it thinks there isn't sufficient boost.

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          #5
          Originally posted by '84 Bronco II View Post
          Assuming the other trucks are Superduties and aren't manual transmissions, why not try one of the PCMs from those trucks? The hardware is the same to my knowledge regardless of PCM strategy. Sorry, I don't have a spare PCM for you to try, but I doubt it is the PCM anyways.

          Have you connected an independent pressure gauge to the MAP pressure line to verify that the MAP sensor is seeing actual manifold pressure? I'd suspect a boost leak on the MAP line causing the sensor to only see near ambient pressure and the PCM to not fuel as it should since it thinks there isn't sufficient boost.
          one super duty is zf6 and the other is an excursion with pats and I dont know how thatll play along with being swapped and since thats my daily dont really wanna fuck it up. Its a possibility that it could be the hose from the spider to the map, although ive checked it with that line unhooked and still saw the same 12.2psia. Im starting to lean towards it having something to do with the resistance in the signal wire, Ive pulled the PCM and it has been replaced previously(probably chasing this same problem). Ive checked the voltage of the signal wire at the plug and both my excursion and the dump read the same(dont recall off hand what it was). So pretty confident the problem is somewhere between the plug and the PCM or the PCM itself, never had a bad PCM in anything ive owned though.

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            #6
            If the MAP pressure line is not getting pressure to the MAP sensor, then you shouldn't see any difference with the pressure line disconnected. Get a pressure gauge and hook it to the MAP line and go drive around. If your MAP line is pressurizing like it should you should see it on the gage. If not, it will just read ~ambient pressure like your MAP sensors. The fact that the truck runs well with the MAP unplugged electrically tells me that the truck is running fine, it just isn't getting a pressure signal to the MAP sensor. The computer just uses tables to infer what the MAP pressure is based on other parameters.

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              #7
              The PCM from a ZF-6 truck will not work, nor will an Excursion PCM. The ZF-6 has no transmission strategy programmed for the 4R100 and the Excursion uses a Glow Plug Control Module that will not fire a standard GPR.

              If the PCM is bad the truck will not run at all. It sounds like you have some boost leaks somewhere. MAP controls fuel via Boost PSI, if there is a bad enough leak it wont build enough to tell the computer to fuel more. These trucks also have about 20 leak points on the intake and exhaust side. The best way is to build a boost leak tester to find out where it is leaking. The PMT2 PCM also has some very reserved low RPM fueling that can make it seem worse.

              Up-pipes, Exhaust Manifolds, Intake Spider, Intake Plenum, Intercooler Boots, Bad T-bolts, V-bad clamps, Small Rubber hoses (MAP) all are suspect to leaking. Another possible thing to look at is the wastegate actuator. If it has become disconnected it wont build any boost.

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                #8
                Originally posted by back woods View Post
                The PCM from a ZF-6 truck will not work, nor will an Excursion PCM. The ZF-6 has no transmission strategy programmed for the 4R100 and the Excursion uses a Glow Plug Control Module that will not fire a standard GPR.

                If the PCM is bad the truck will not run at all. It sounds like you have some boost leaks somewhere. MAP controls fuel via Boost PSI, if there is a bad enough leak it wont build enough to tell the computer to fuel more. These trucks also have about 20 leak points on the intake and exhaust side. The best way is to build a boost leak tester to find out where it is leaking. The PMT2 PCM also has some very reserved low RPM fueling that can make it seem worse.

                Up-pipes, Exhaust Manifolds, Intake Spider, Intake Plenum, Intercooler Boots, Bad T-bolts, V-bad clamps, Small Rubber hoses (MAP) all are suspect to leaking. Another possible thing to look at is the wastegate actuator. If it has become disconnected it wont build any boost.
                The PCM maybe good but whatever chip digests the MAP sensor voltage may not be, which Im starting to believe is the issue. Ive jumped around the signal wire from the plug right to pin 79 and continuity straight through. Got 12.33PSIA this time. All new manifolds, up pipes, non-ebvp pedestal and turbo housing that side of things should be leak free. But key on engine off it still reads 12.2/12.3PSIA, it could be leaking from all 20 of those intake/exhaust points but key on engine off it should be recognizing the correct atmospheric pressure which its not. The other two super dutys read 14.06/14.08 key on engine off which is correct. The difference between 14.06 and 12.2 is about 4000' so its fueling for 5k while being at 1k resulting in total lack of nut. Also could be the barometric pressure sensor which is part of the PCM is shit and throwing off the map reading(I believe they work together).


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                  #9
                  Might have a clogged EBP (Exhaust Back Pressure) Tube and/or bad EBP sensor.

                  Good info here.
                  https://deadheaddiesel.com/ebp-senso...essure-sensor/

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                    #10
                    *****update*****

                    I got my hands on an NVK3 pcm, all is well. Just under 14psia KOEO, boosts properly now and MAP changes accordingly. Brake boosting itll blow the tires off on dirt now where as before to the floor it couldnt even push through the brakes.

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                      #11
                      Originally posted by Smokewrench View Post
                      *****update*****

                      I got my hands on an NVK3 pcm, all is well. Just under 14psia KOEO, boosts properly now and MAP changes accordingly. Brake boosting itll blow the tires off on dirt now where as before to the floor it couldnt even push through the brakes.
                      Glad to see you got it figured out, sorry for doubting your original diagnosis.

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                        #12
                        Originally posted by '84 Bronco II View Post

                        Glad to see you got it figured out, sorry for doubting your original diagnosis.
                        Not a problem at all, I was skeptical of it being the PCM at first too.

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