Detection Condition

PCM compares the number of HO2S (front) and HO2S (rear) inversions for a predetermined time. PCM monitors number of inversions rear side HO2S performs while front side HO2S inverts for a specified number of times when monitoring conditions are met.

Monitoring Conditions

• Calculated load is 15-48 percent (Maximum calculated load value varies depending on engine speed.)
• Engine speed is 1500-3000 RPM.
• Vehicle speed is 17.3-74.5 MPH.

PCM detects inversion ratio. If inversion ratio is less than threshold, PCM determines catalyst system has deteriorated. This is an intermittent monitor. MIL is illuminated when PCM detects malfunction condition in 2 consecutive drive cycles. Pending code is available if PCM detects malfunction condition during first drive cycle. Freeze frame data is available and DTC is stored in PCM memory.