Manual swap and now getting a p0720 and p0722 - Ford Mustang Forums : Corral.net Mustang Forum
 
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post #1 of 8 Old 06-17-2019, 03:53 PM Thread Starter
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Manual swap and now getting a p0720 and p0722

Hey guys, after my manual swap (99 v6 4r70w to 03/04 t56) the speedometer stopped working and I am running into a P0720 and P0722 code. I am using a t56 wiring harness and the o2 sensors/etc work, but the speedometer is not working at all. I replaced the speed sensor but that didn't fix the issue.
Does anybody have ideas on how to properly troubleshoot this or know what wires I can splice to get things working? I have one of the Ford wiring diagrams but I can't figure out where each of the wires end up from the sensor.

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post #2 of 8 Old 06-17-2019, 04:04 PM
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Do you have the harness for the 4R70W and can verify that you have pinout conductivity from the speedo sensor to the main connector pins?


1994 Ford Mustang GT
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1992 Ford F150
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post #3 of 8 Old 06-17-2019, 04:15 PM Thread Starter
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I think you're on to something. After you said that I found these two posts about the issue:
https://www.modularfords.com/threads...56-swap-wiring
https://www.modularfords.com/threads...ness-info-here

I'll check out the harnesses tonight and hopefully it's an easy fix
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post #4 of 8 Old 06-17-2019, 09:37 PM
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ford changes pinouts all the time

when you do something like this you need a wiring diagram to complete circuits.

89 GT gr-40, KB2200(10psi), tweecer R/T,LC-1, 22gal cell, w/tailpipes.
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post #5 of 8 Old 06-18-2019, 01:40 AM Thread Starter
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I have the Ford Wiring Diagram book for the 2000 Mustang but not for the 03/04. Would anybody happen to have a copy and could scan a couple of pages for me? If not, I'll just go through the harnesses wire by wire.
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post #6 of 8 Old 06-18-2019, 10:13 AM
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What about using your harness, and swapping pigtails if yours doesn't plug into the new trans?

1994 Ford Mustang GT
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post #7 of 8 Old 06-18-2019, 10:28 AM Thread Starter
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That's what I'm going to end up doing, just gotta figure out each wire and solder it. I already figured out what wire is what, just need to use my book to figure out which ones are for the reverse light. It's gonna be a lot of soldering over the next day or two.
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post #8 of 8 Old 06-20-2019, 12:08 PM Thread Starter
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Good news, on Monday I swapped the pigtails and got to test the car out yesterday...It worked!! Speedo is working, reverse lockout is solid, and everything is good to go. The only problem I'm having is with the reverse light. I tested it while I was soldering and it worked while supplying 12v from another source, so I think it's just not getting the proper power...easy fix that I'll take care of later.
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