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Home >> Toyota >> 2003 >> Matrix Base, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 103 (Engine Control System Self Diagnostics) >> Diagnostic Tests >> DTC P0420: Catalyst System Efficiency Below Threshold >> Possible Causes
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Possible Causes

WARNING: This page is about a different car, the 2003 Toyota MR2. However, it is still accessible from the selected car via links, so may be relevant.

DTC is set when both oxygen sensors have same amplitude after vehicle is driven for 5 minutes at 20-50 MPH. Possible causes are: