What do i need to do to repair this problem?

Question

2003 Pontiac Grand Prix GT 3.8 L no supercharge

Answer 1

p0420 Catalyst Efficiency Below Threshold (Bank 1)- most like the catalytic converter needs to be places if the oxygen sensors are fine.

P0650 check to see if your fuel pump is working correctly, it should be around 35psi with the car in idle. if that is fine there is a problem with the Malfunction Indicator Lamp, could be bad/short wire.