Can replacing spark plugs fix error code PO420

Question

Car just passed inspection for emmisions

Answer 1

p0420 usually means a bad catalytic converter on bank 1 

its possible for the spark plugs to cause the light to go on but you would also have a misfire code with the P0420 

 

Possible causes

- Three way catalyst converter Bank 1

- Exhaust tube

- Intake air leaks

- Fuel injectors may be faulty

- Fuel injector leaks

- Spark plugs may be faulty

- Improper ignition timing

- Engine Control Module (ECM)