Detection Condition

WARNING: This page is about a different car, the 2003 Mazda 6. However, it is still accessible from the selected car via links, so may be relevant.

PCM compares number of front HO2S and rear HO2S inversions for a predetermined time. PCM monitors number of inversions rear side performs while front side inverts for a specified number of times when following Monitoring Conditions are met. PCM detects inversion ratio. If inversion ratio is less than threshold, PCM determines catalyst system has deteriorated.

Monitoring Conditions:

Calculated load 15-50 percent (maximum calculated load value varies depending on engine speed)
Engine speed 1500-3000 RPM (MTX)
Engine speed 1410-3000 RPM (ATX)

This is an intermittent monitor (CATALYST). MIL illuminates if PCM detects malfunction condition in two consecutive drive cycles or in one drive cycle while DTC for same malfunction has been stored in PCM. PENDING CODE is available if PCM detects malfunction condition during first drive cycle. FREEZE FRAME DATA is available. DTC is stored in PCM memory.