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Home >> Mitsubishi >> 2003 >> Lancer Evolution >> Repair and Diagnosis >> External Pages >> Different car >> Section 30 (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 >> Possible Causes
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Possible Causes

WARNING: This page is about a different car, the 2002 Nissan Maxima and 2002 Infiniti I35. However, it is still accessible from the selected car via links, so may be relevant.

Malfunction is detected when switching frequency of HO2S2 increases to a specified value, indicating that warm-up 3-way catalyst is not operating properly. Possible causes are: