The error P0203 Code is a powertrain problem and it is found in the car engine problem. The description of the car engine code is the catalytic converter has an oxygen sensor in behind and front it. When the car is heartfelt and running in locked loop mode, the upstream oxygen sensor waveform interpretation should alter. The engine can be fixed according to the valves of apiece cylinder are remained closed using a pair of arms that substitute the conservative engine’s roller-type rocker arm. The engine P0203 code is one of these arms follows the cam profile when the 2nd arm joins to the valves. During normal engine operation the 2 arms are joined by a locking pin.