This Preliminary Information communication provides information to the technician of additional information while diagnosing a diagnostic trouble code P0420. Check for a possible leak in the exhaust system behind the bank one number 2 oxygen sensor. If a leak is found or there is an aftermarket utility bed or trailer hitch installed. Check for a minimum clearance of 1.5 to 2 inches of the exhaust system. Install a new clamp and torque it to 40.5 foot pounds.