I started getting codes p0121 tps 1 performance & p0122 tps 1 low voltage. I replaced throttle body was fine for about 3 months than started throwing codes again, got a warranty replacement no fix, check voltages with scan tool and oscilloscope at throttle body, voltage fine with engine cold, but as it warms up, they slowly start dropping as the engine warms up, till its fluctuating between. 3 and 0 volts, thought maybe it was the cheap throttle bodies off Amazon so purchased a used one, same result. Not sure where to go next, pcm?