2007 Scion tC check engine light on

after i install a cold air intake in my car the check engine light came on, i check for the code and was p0101, to make sure that wasn't the sensor i put back the old sistem and the light stay off,
then i put back the intake and after 15 mile came back on, i tried disconecct the batery and nothing, after a drive like 15 to 20 mile came back on.

what else i can do.
thank