toxicchevy393

so i replaced both my down stream o2 sensors on my 2000 silverado 1500 with the 5.3L and they both are reading lean ( codes P0137 and P0157 ) , pretty much what can cause this and or my other thought is i just got a hypertech programmer for it, i used it to read the codes but did it set off the codes too? can a programmer do this? if not what should i check or test? thanks o and also (code P0221 ) "Throttle/Pedal Position Sensor/Switch 'B' Circuit Range/Performance Problem" is coming up too, could the code p0221 be whats causing the other 2 codes to come up? or the programmer causing all 3 or has nothing to do with it, any info on any of the above is greatly appreciated, thanks

toxicchevy393

so i just went and redid the engine codes and all of the abover were still ther but an addtional one was also there, DTC P1637, generator L terminal circuit, i have no clue what that means or if it has anything to do with the above, but also any advice on this would be good to, imagine it has something to do with the alternator, assuming generator=alternator correct?