Never had any problems with the car. Couple weeks ago started a loud tap or lite knock. Was Going to adjust the values. Then check engine light comes on. Scan tool said codes p0240 catalyst system efficiency below threshold B1 and code p1659 ETCS control relay off malfunction. Was told p0240 was catalytic converter which is 4 hundred .need help to know what the codes are and how to check to see what is actually happening. Wondering could the tap have something to do with the code. Would appreciate help in what steps to take before buying expensive parts for no reason. Highly appropriate any insight.