Do not drive the car when you detect any problem in the car engine and the engine code P203C OBD2 may also be caused by faults earlier down the line of the car engine problem. Suppose, a dirty MAF sensor might be instigating the car to overreact in its fuel-trim changes. As a result, oxygen sensors are probable to report fuel combination glitches. The P203c engine code seems a kind of powertrain problem of the car engine and this problem can be solve easily. Once the car engine is ok, you can drive the car properly. Make sure that the car engine is ok.