HELP! P2105 and U0300 codes after custom tune
 

I recently had PHP do a custom tune 91 performance for me and just installed it last week. It worked great for me until just last night I was driving home and at around 50mph the tranny started slipping out of gear and i freaked out because I knew that was not a good sign because I had that happen to me when my transmission went out and I just replaced it about 6 months ago from the Ford dealership (ouch - big money) So i know that it is NOT the transmission going out. I pulled over and checked the codes and P2105 - throttle actuator control system - forced engine shutdown and U0300 - internal control module software incompatibility. I was pissed (still am) so i returned the truck back to stock thinking that it would fix the problem but the tranny keeps slipping - I know it is NOT the transmission. I've researched as much as I could and can only find that the Throttle Position Sensor might be bad and the throttle body might need to be replaced or the PCM needs a reflash or possibly needs replacing. However, this happened way too close to the install of the custom tune so I call BS. Can anyone help me? I know PHP takes forever to try and respond. I've already tried e-mailing and calling. I don't mind replacing the throttle body and throttle position sensor if thats really the case but I don't want to start throwing money and trying a trial by error fix cuz i might be in 1500 or more after i'm done. Thanks.

If you're still having the problem at stock, then it's not the tune. I notice you have a CAI on your truck. What year is the truck? I'm guessing it's not a new model. CAIs on the 04-05 trucks especially can cause the engine to run lean.

Are the throttle body and MAF sensor clean?

And, even if the transmission was replaced 6 months ago, it could well be going bad again.

- Jack

I have emailed the customer and contacted Bill about this.

I've experienced a "slipping" feeling in the low rpms of 4th gear, around that 45 - 60 mph range.

I've got an '04 F150 5.4L and when I would cruise around in 4th and lightly accelerate, the truck would "shudder" or feel like the transmission was slipping, but I could always gas out of it and the truck would drop to 3rd gear, ceasing to shudder.

No one could figure it out until 1 day, the check engine light came on and the truck started misfiring. 1 new ignition coil later and my 4th gear slippage disappeared.

It's happened 3 times in all in the span of 2 years. When the truck starts to "slip" in 4th gear, my mechanic can find a coil that is bad.