Transmsision Code PO715

[GordonL]

I have a 97 Taurus which I ended up with as a favor to a friend. Transmission was bad so I replaced it with a junk yard unit. Before I replaced it there was a code PO715 (input/turbine speed sensor A circuit malfunction) and a couple of others but the transmission guy at the dealer assured me that the transmission was bad. After putting in the new transmission I again get the PO715 code. Can I have something as simple as a bad sensor or a bad wire? How do I diagnose this?

[shorod]

According to the factory service manual, that code indicates that the PCM detected a loss of Turbine Shaft Speed (TSS) sensor signal during operation. This issue could certainly be due to a faulty connection or wire between the PCM and the sensor. FSM Pinpoint Test F for the transaxle gives quite a few steps for troubleshooting this code.

-Rod

[GordonL]

Thanks: I still have the old transmission so I could also replace the sensor. Any idea of how to replace it? I do not see an obvious way to remove it. Car also shifts hard from 1 st to 2nd. Would that be related?

[shorod]

Which transmission do you have, the AX4N or the AX4S? If you have the 3.0L 12V, you could have either. If you have the 24V Duratech or the SHO, it will be the AX4N.

It appears that in either application, the TSS is located near the driver's side axle on the side of the transmission, a bit behind the side cover. There's one bolt holding the sensor in (torque to 80-106 in-lbs). The FSM suggests removing the battery and battery tray to gain access to the sensor, but it looks like it should be accessible from the wheel well or underneath the car. Maybe someone with more transmission experience can answer this. Also, I guess you could find it on the removed transaxle and determine where it would be on the car.

But, as I mentioned in my previous post, your code could be caused by a wiring issue. It's unlikely that the TSS in both transaxles would have failed in the same way, from reading posts on this forum for almost 5 years I don't recall anyone needing to replace their TSS.

-Rod

[GordonL]

I have the AX4N. It is on the top of the transmission right next to the selector harness, I agree that it is unlikely that the sensor is bad. Nothing obviously wrong on the wires. Any thoughts on hard shift from 1 to 2? Any connection?

[shorod]

Yes, according to the FSM, harsh shifts can be attibuted to a faulty TSS connection/signal.

-Rod

[tripletdaddy]

Mine seems to go into gear hard when at idle going into F or R. Could that also be the TSS or its wiring? I've always thought it engaged much too hard. The idle is correct. 95, 3.8, 85k, but been doing it for long time.

[shorod]

Originally Posted by tripletdaddy

Mine seems to go into gear hard when at idle going into F or R. Could that also be the TSS or its wiring? I've always thought it engaged much too hard. The idle is correct. 95, 3.8, 85k, but been doing it for long time.

I suppose it could be, but I'd more likely suspect worn engine or transmission mounts if it shifts fine otherwise.

-Rod

[GordonL]

Finally found the problem. The TSS was not plugged in all the way. Pushed it fully on and the car shifts just fine. Thanks for your help.

[shorod]

That's excellent news. Thank you for the follow-up with what you found, it helps make this forum much more effective.

-Rod

[tripletdaddy]

Mine shifts smoothly during normal gear shifts and hard accelerating. Only when going from P to F, or N to F or to R does it engage hard, like the rpm was way up, but it's not. When I'm under it next time, I'll check the TSS connector. I haven't noticed any tell tale signs of the mounts being loose or worn, but I can easily check that. The car with about 40k miles needed the front motor mount replaced. It just pulled apart. Does anyone know if that's a common failure on the 3.8 and if it's something Ford knows about? I sure couldn't believe it happened. It must have been defective, though I don't recall it having any obvious flaws in the the rubber.