Possible Causes

This DTC uses two-trip detection logic. DTC is set when A/F sensor and heated oxygen sensor have nearly the same waveform pattern after engine and catalytic converter are at normal operating temperature and vehicle is driven. Possible causes are:

• Exhaust system leak.
• Defective A/F sensor (B1 & 2 S1).
• Defective heated oxygen sensor (B1 S2).
• Defective three-way catalytic converter (TWC).