automatic transmission position sensor bypass

Discussion in '2005+ Mustang GT 4.6L Tech' started by Sean M, Dec 2, 2020.

  1. Sean M

    Sean M Junior Member

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    I am finishing up a swap from a 2007 GT manual into a 2005 automatic chassis. I moved the engine, pcm, wiring harness, transmission, pedal box and drive shaft. I also switched over the old key cylinder to bypass the PATS. Everything looks pretty good so far and the antitheft light went out thanks to some advice from other members here. I am running into a stumbling block on getting it to start. I think the problem is likely the automatic transmission position sensor, which is probably looking for the car to be in neutral. Does anyone know a way to bypass that?
     
  2. 07 Boss

    07 Boss Senior Member

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    If you switched the pcm and harness why would it look for a signal from the position sensor? Wouldn't it be looking for signal from the clutch?
     
  3. Sean M

    Sean M Junior Member

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    I only moved the wiring harness going to the engine and transmission. I was hoping not to have to move the wiring going to the dash, as that would be a major pain. But I guess I might have to move all of that wiring also. It looked to me from the wiring diagram that the wiring went from the ignition to the position sensor and then to the PCM. So I was wondering if just splicing the wire going into the sensor to the one going out of it would bypass that. I wonder if the clutch pedal position switch can be turned off with a tune.
    Thanks,
    Sean
     
  4. Joe combs

    Joe combs Member

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    if the neutral safety is off in position it will not start. I have done this swap, and did not change any off the harness other than what you did. I would disconnect the shifter cable at the shifter, make sure it is is neutral, using the cable make sure that the transmission is now in the neutral position, then reconnect everything. if it is off just a little bit it will not start... if you swapped the engine pcm and wiring it will not be looking for the clutch position sensor, so you dont have to worry about that
    You didnt mention swapping the smart junction box, as the manual transmission programmed SJB will not see your foot on the brake pedal and allow the car to come out of gear.
     
  5. Sean M

    Sean M Junior Member

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    Thanks for the response. It was in neutral when I disconnected I did not switch the smart junction box. Are you saying that I should switch the sjb?
     
  6. Joe combs

    Joe combs Member

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    there are differences in the harness pinout between a 05 and a 07 so that is likely your issue. you could swap the SJB from the 07, but the 07 was set up for tpms and may look for those sensors once plugged in. I think your problem is going to be the body harness talking to the newer 07 engine harness. I was originally reading this as going from manual to auto... what the pcm is looking for is the clutch pedal position sensor telling the pcm the pedal is pressed in, the sjb you have is for an automatic... so it is looking for the automatic gear shift to be in park. would try swapping the sjb... but i also dont think you are going to have anything connected to the clutch pedal position sensor, so it isnt going to crank over...
     
    Last edited: Dec 5, 2020
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