Possible Causes
WARNING: This page is about a different car, the 2003 Nissan Pathfinder. However, it is still accessible from the selected car via links, so may be relevant.
ECM illuminates MIL and sets DTC P0420 when switching frequency of HO2S increases to a specified value, indicating that Bank 1 warm-up 3-way catalyst is not operating properly. ECM illuminates MIL and sets DTC P0430 when switching frequency of HO2S 2 increases to a specified value, indicating that Bank 2 warm-up 3-way catalyst is not operating properly. Possible causes are:
- Defective warm-up 3-way catalyst (exhaust manifold).
- Exhaust leak.
- Intake air leaks.
- Defective injectors.
- Defective spark plugs.
- Incorrect ignition timing.
- Poor, loose, corroded or damaged terminal connections.