well when it was flashing a 4,3 that is a thermal cutback code
replacing the tpa board was a final solution if code did not clear

as for the 2,1 code this is a throttle wiper input fault
corrective actions:
step1- set vom to dc volts, pos lead on JPT11-5, neg lead on JPT11-6
full speed request = 4.25v, no travel request 0 volts.
If it passes test replace STM
step2- set vom to dc volts, pos lead on J1-6, neg lead on J1-7
Full speed request = approx. 4.25v, No travel request = 0v.
if passes replace TPA, if fails troubleshoot wires from STM.

check your connections and wiring first, then run the above test to see of this STM is bad or just connected incorrectly.