My wife and I both have 2005 mustangs. Both are GT 4.6. Her battery died and would not start the car. I replaced the battery with a Optima red top and car started. Unfortunately the vehicle will only idle at this point and is in failsafe mode. I pulled the codes off of the computer and had a P2104 and a P2112. When I bought her car it did not have a stock ford throttle body on it. Someone had replaced the original throttlebody with an aftermarket unit and cold air intake. I have removed the throttlebody and cleaned and inspected. Cleared the codes. Both of the codes come right back. Tab opens and closes with motor not running.

 

Try tightening the idle adjustment screw on the throttle.

 

Adjusting ref voltage?

 

If you're going into limp before the engine starts(ie, the wrench is illuminated initially in the run position before starting) with those codes it's normally because you are failing the throttle checks. If the TPS is faulty it could be causing your closed position ref voltage to read too low which would throw it into Limp. Tightening the butterfly stop screw could jury rig it.

If your actuator is faulty or binding, it would fail the IAC logic in the DBW and it will force idle into limp mode.

Honestly, if it's an option, I would just get a stock throttle body and put on the car. The s197's drive by wire does not seem fond of aftermarket throttle bodies mainly those "no tune required" throttle bodies.

Idle screw, TPS, Actuator, back to stock throttle body, is the order I'd go with in diagnosing.

 

Sounds like the aftermarket throttle body is throwing the ECU into failsafe mode. The reason could be that either the TPS voltage isn't set correctly, the TPS is faulty, or the throttle actuator is faulty.
If adjusting the TPS voltage to the stock setting doesn't solve the problem, I suggest you just buy a good used stock throttle body and swap it in.

 

Yes, that is exactly what was taking place. Reference voltage from PCM was at 5.03 V. Signal wire number one was a .6 V . Signal number two was 4.68. Attempted to adjust throttle stop screw, 2.5 mm Allen and metal screw seized in aluminum threads. Also, plunger on in the throttle stop seemed in operable. Pooled stock 55 mm throttlebody off my other car and donated to wife's car. Changing Throttlebody seem to fix call. Voltages came back into range. When you use a custom tune on an aftermarket throttlebody is it possible to change the values of acceptable voltages required by PCM? And example good they have set the low side to .6 to accommodate for a position of fly plate when you use a custom tune on an aftermarket throttle body is it possible to change the values of acceptable voltage is required by PCM? In example good they have set the low side to .6 to accommodate for a position of fly plate . Thanks for all the great advice.

 

Sorry 4 typo's......won't let me edit at this point