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Home >> Infiniti >> 2003 >> FX45 >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0420: Catalyst System Efficiency Below Threshold (Bank 1) Or DTC P0430: Catalyst System Efficiency Below Threshold (Bank 2) >> Circuit Description

Circuit Description

The ECM monitors the switching frequency ratio of Heated Oxygen Sensor (HO2S) 1 (front) and 2 (rear). A 3-way catalyst with high oxygen storage capacity will indicate a low switching frequency of HO2S2 (rear). As oxygen storage capacity decreases, HO2S2 switching frequency will increase. When the frequency ratio of HO2S1 (front) and 2 (rear) approaches a specified limit value, the 3-way catalyst malfunction is diagnosed.

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