Possible Causes

Malfunction is detected when switching frequency of HO2S2 increases to a specified value, indicating that 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.