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Home >> Mazda >> 2002 >> Tribute LX, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 59 (Engine Controls - Self-Diagnostics) >> Diagnostic Tests >> DTC P0421 Or DTC P0431 >> Detection Condition

Detection Condition

WARNING: This page is about a different car, the 2003 Mazda MPV and 2002 Mazda MPV. However, it is still accessible from the selected car via links, so may be relevant.

PCM compares number of front Heated Oxygen Sensor (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:

Monitoring Conditions

PCM detects inversion ratio. DTC is set, if inversion ratio is below threshold. This is an intermittent monitor. MIL is illuminated if PCM detects malfunction in 2 consecutive drive cycles.