Tremec swap gone bad

[Nsinclair]

I blew the getrag, had a magnum installed with all the proper upgrades to the driveline, it works great. 3 weeks later my Speedo quit working, every light on the dash pretty much came on, and I was sure it was due to the wiring on the new trans. Then suddenly it worked again...and it worked everyday for the following 8 months. Till last week, same issue. I thought maybe it was the signal from the Abbott conversion box, so i bypassed it, still nothing. Read the voltage coming from the output sensor, it's working, as I'm getting AC volts as I turn the wheels. My little code reader says output shaft speed sensor circuit. But sensor is working. So this leads me to can bus, or the pcm? Any ideas?
I priced a pcm at Ford for 600
No idea how to price a can bus system
2012 mustang gt premium
Dyno tuned at performance evolution

 

[2013sTang]

Did you do the swap yourself or done at a shop? If at a shop you may want to call them up

 

[Nsinclair]

At a shop, and they're looking into it, but the stuff he installed is all in working order it seems. Just frustrated that a PCM could be bad in a 2012

 

[crjackson]

Check for harness damage.

 

[cyclerick]

It's the speed sensor cable (or whatever it's called) that attaches to the transmission. I had same issue, no speedo or wrong speed, all dash lights come on, dash changes colour. I would hit a bump and then speedo worked properly and then it would quite. What was happening is that the speed sensor cable was not snapping in place on the Tremec. Once I replaced the cable it worked perfectly.

 

[Nsinclair]

I'll double check that cable again, hopefully it's that! Worked the last two days and worked when I parked car, and wasn't working on the way home. Getting super frustrating

 

[Nsinclair]

Checked harnesses, everything is weatherpacked very nicely still. Nothing exposed, and all connections are locked into each other tight. Using a multimeter on the cable from the tremec I'm getting ac volts when rotating the wheels.

 

[Eel Mit]

Could also be the plastic driven gear in the trans is broken (stripped teeth).

 

[Nsinclair]

Had my tuner use his laptop on it today. 9 codes for loss of connection to instrument cluster from all kinds of different modules. We're not sure if that's from the trans or its own problem

 

[Nsinclair]

Just wanted to update this, we found what seems to be the problem. The Speedo conversion box from Abbot has been bypassed and then the computer tuned for the output shaft difference and 0 problems yet with connection issues.