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The P0401 code can be from a plugged EGR tube or port, however I don't know if that will cause the P0420 code. Here is some info for both of the codes:
http://repairpal.com/OBD-II-Code-P0401
http://repairpal.com/OBD-II-Code-P0420
The codes are T0420 and T0401
The P0401 code can be from a plugged EGR tube or port, however I don't know if that will cause the P0420 code. Here is some info for both of the codes: http://repairpal.com/OBD-II-Code-P0401 http://repairpal.com/OBD-II-Code-P0420