Chevrolet Repair: 96 CHEV CAVALIER, crankshaft position sensor, timing light

Question
I AM GETTING COED PO335 (CRANKSHAFT POSITION SENSOR A CIRCUIT MALFUNCTION) AND CODE P0342 (CAMSHAFT POSITION SENSOR A BANK 1 CIRCUIT LOW INPUT) AND P0420 (CATALYST EFFICIENCY BELOW THRESHOLD )... I CAN REPLACE THE SENSORS BUT IS THE TIMEING CHAIN GOING OUT ?

Answer
Excellent assumption!!
Dont replace the sensors, chances are they are still good.
Throw a timing light on it (just to make sure)and if it jumps around, you've found the problem. You should be able to reconnect the battery after replacing the belt, and the check engine codes should be taken care of.