Make sure that the IAT sensor is plugged in, if you have an 03 it will be in the air box with an 02 it is under the injector in the front head. That is unless you have done the update kit with the relocation to the air box cover. You can ohm the IAT sensor out and the electronic manual has the ranges that it should be in it but a bad one will usually read open. If you have had the relocation kit done make sure to check the wiring at the point that the connection for the plug was made.
Max