LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Mitsubishi >> 2003 >> Lancer Evolution >> Repair and Diagnosis >> External Pages >> Different car >> Section 54 (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
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Possible Causes

WARNING: This page is about a different car, the 2002 Nissan Xterra and 2002 Nissan Frontier. 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 3-way catalyst is not operating properly. Possible causes are: