Anybody knows how can i fix scanner code p2138 , truck check engine light came on also engine power is reduced.

 

It's probably best to take it to a shop. P2138 means an invalid correlation between PPS #1 and #2. The APP sensor consists of two pedal position sensors which are basically potentiometers that return variable voltage levels to the ECM. The ECM then sanity-checks one input against the other. When it detects a sufficient difference between the two, it can't trust the calculated accelerator pedal angle and thus goes into limp mode. Just so you don't go throwing parts at it, the cause is not always the APP sensor itself.

 

What year model of vehicle? if its an 07, several folks over in the Tahoe/Suburban forum have been replacing the TPS that is attached to the accelerator pedal for a similar issue if I recall...or it could have been the throttle body...
you may want to try disconnecting the battery to clear the codes and reset the ECM and BCM and see what comes back...