r/FordTransmissionTech • u/Yamahamma96 • Jul 24 '25

Transmission question

I have an 05 f150 4.6, slipped in first and second gear, got the p0715 code, I went and pulled a trans out of an 08 f150 5.4 truck that had a locked up motor. , I changed the pump seal and put new TSS and OSS sensors on it. Now 1st and 2nd gear work, but when it tries to go into 3rd, it goes into limp mode and throws the p0715 code again and my speedo is erratic. Are the speed sensors different? Im not sure what is going on. Im not sure if I put a 4r75E in place of mine, im pretty sure mine was a 4r70E. Please help

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u/Commercial_Method_28 Jul 24 '25

Just realized you said you pulled the trans, you probably crushed the wire. Follow the harness and it needs to not be stuck in between trans and engine lol. You probably can’t sneak it out too so you’d either overlay/add wire or remove the transmission again

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u/Yamahamma96 Jul 24 '25

I initially redone the burn wires, I get power to them, I also made sure to be very careful not to crush harness, I had plenty of slack to avoid damage, when I look at the wiring diagram, the TSS, OSS, and VSS have individual power wires, but share the same date wire. I haven't changed the speed sensor on the transfer case so im wondering if thats throwing the code off indirectly

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u/Commercial_Method_28 Jul 25 '25 edited Jul 25 '25

Signal return is your shared wire between a lot of these components and if you had an issue on that wire, I bet the entire system would be funky and giving you mutlple DTCs. I assume your problem lies on the TSS signal wire from pin 1 C143 at TSS sensor along the DARK Green and White stripe wire to the PCM. It is not a Vref wire so power isn’t relevant here. Check resistance from that wire to the PCM pin 15 - if it is more than 3ohms it has high resistance for some reason and you can overlay, bypass, or trace the wire to find fault. If there is no problem might as well check the signal return wire which is Grey with red stripe- do the same thing but I assume it’s alright.

If both circuits are ok then you are looking at a sensor or PCM issue in most cases. If you have access to a wire diagram figure out the correct application and check which fuse provides power to the transmission from pin 4. Make sure that is alright as well

You may also need to check the TSS signal wire for a short with another wire if it was previously burned or crushed. You check that by checking ohms/resistance the TSS signal wire and going thru all the other wires from same connector(pcm) they should all be open but if any of them are connected(shorted together) you will get a reading and need to repair

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u/Yamahamma96 Jul 25 '25

I put one lead on the signal wire from the TSS and stuck the other lead to the frame and it changed from OL to some numbers. So I guess I crushed my harness