P00F9 Paterson Model 33 is a DTC or a diagnostic trouble code. It is a check engine light code which indicates that the catalyst's system efficiency is less than the required threshold. In simple terms, it means that more pollution is added into the air than what was supposed to be because of your car. As you drive and when specific conditions are slowly met, the vapors will gradually purge from the charcoal canister and will get burned within your engine.
Possible Causes :
Find out what kind of system you have and verify that voltage to the fuel level sensor is present at the fuel pump wiring harness. Replace the oxygen sensor that is downstream from the catalytic converter on the side of the engine that does not contain cylinder #1. Also, if a oxygen sensor code stating "heater circuit malfunction" the sensor has most probably failed. If you find a related TSB, the information will often help in diagnosing the code in question as TSBs are crested from many thousands of repairs.
Diagnostic trouble code P00F9 Paterson Model 33 is not difficult to diagnose and repair. Thus, it always pays to have a qualified technician to look after your vehicle should this error code arise.
Diagnosing this code requires the engine to be in good running shape, without unmetered air entering the engine. If other codes that relates to misfiring condition, lean running or air entering the engine is present, then you must first fix those error codes before P00F9 Paterson Model 33.
Fortunately, P00F9 Paterson Model 33 is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.