Detection Condition

PCM monitors inversion cycle period, lean-to-rich and rich-to-lean response time. PCM calculates average response time during Drive Mode 3, when monitoring conditions are met.

Monitoring Conditions

• Calculation load: 26.6-57.8 percent depends on engine speed.
• Engine speed: 1500-2500 RPM.
• Engine coolant temperature is more than 14°F (-10°C).

If response time exceeds threshold, PCM determines HO2S circuit has malfunction. This is an intermittent monitor. MIL is illuminated when PCM detects malfunction in 2 consecutive drive cycles.