actually the 2 tps sensors measure the whole throttle range, one goes from higher voltage to lower voltage and the other the opposite (from lower voltage to a higher voltage), to insure that each one is operating correctly. the code 638 would indicate the throttle unable to close completely, so you may want to first check your throttle cable and make sure there is nothing restricting the plate from closing.
There is two tps sensors on the spectrum system one to measure throttle open and thro5le closed
liftv5, I am having the same code as far as 638 I have replaced the TPS and still cant get the code to clear watching it the tps command drops out and the truck dies and kicks that code any ideas
ok so I didn't read the part where it says code 166 means the system is correctly completed the self test portion found the answer in search here on website thanks guys