I have a 99 SC400 with irratic idle problems and it is stuck in "limp mode", where you have to mash the pedal to the floor in order to get it to move. Autozone coded it as the TPS sensor. I replaced it with no resolution. I've read some posts and it sounds like it could be the Acellerator Position Sensor or the Throttle Control Motor, both of these items run about $300 each! Is there anyway I can find out for sure if its the AP sensor or the Throttle Control motor? I hate to replace both if not needed. I would appreciate any help!