DTC P0421-00; Catalytic Converter System: Notes

NOTE:

To determine the malfunctioning part, proceed with the diagnostics from "Function Inspection Using M-MDS".

Details On DTCs

DETECTION CONDITION AND POSSIBLE CAUSE

DESCRIPTION	Catalytic converter system
DETECTION CONDITION	Determination conditions	The PCM detects that the HO2S output fluctuates from lean to rich in a short amount of time at specified times continuously after recovery from fuel cut control.
	Preconditions	Catalytic converter (WU-TWC) is activated sufficiently. A/F sensor is activated sufficiently. HO2S is activated sufficiently. The following DTCs are not detected: Misfire: P0300:00, P0301:00, P0302:00, P0303:00, P0304:00 Fuel injection correction: P0171:00, P0172:00, P2096:00, P2097:00 A/F sensor: P0130:00, P0131:00, P0132:00, P0133:00, P0134:00, P064D:00, P2237:00, P2243:00, P2251:00 HO2S: P0137:00, P0138:00, P013A:00, P013B:00, P0140:00 A/F sensor heater: P0031:00, P0032:00 HO2S heater: P0037:00, P0038:00
	Drive cycle	1 (U.S.A.) 2 (except U.S.A.)
	Self test type	CMDTC self test
	Sensor used	A/F sensor, HO2S
FAIL-SAFE FUNCTION	Not applicable
VEHICLE STATUS WHEN DTCs ARE OUTPUT	Illuminates check engine light.
POSSIBLE CAUSE	HO2S malfunction HO2S loose A/F sensor malfunction A/F sensor loose Exhaust system leakage A/F sensor deterioration WU-TWC deterioration or malfunction PCM malfunction