I can give you another hundred possible reasons but it is not going to work. Speculation does not work. When trouble codes are present you need to get them rectified first.
TAC is the actuator meaning it is the motor. Atttached diagrams shows the location of the parts concerned. TYhere are a few codes related to the motor and when motor is working, it does not mean it is good as it could be moving out of specs.
If you are not able to perform the test concerned, then it is best to get them done by professionals who knows how to do it.
Images (click to enlarge)
Wednesday, January 5th, 2011 AT 4:26 PM