P0421 MITSUBISHI - Warm Up Catalyst Efficiency Below Threshold- Cylinders 1-4
- Warm Up Three Way Catalytic converter deterioration or malfunction
- Exhaust system leaks
- Loose front or rear HO2Ss
- Faulty front heater O2 sensor
- O2 sensors harness is open or shorted
- O2 sensors poor electrical connection
There is a factory service recall for the following Mitsubishi Models:
2002 Mitsubishi Lancer
2003 Mitsubishi Lancer
2004 Mitsubishi Lancer
2005 Mitsubishi Lancer
2002−2005 Mitsubishi Lancer Factory Service Recall OBDII Code P0421
When is the code detected?
- Engine Light ON (or Service Engine Soon Warning Light)
P0421 MITSUBISHI Description
A three way catalyst converter (Manifold) with high oxygen storage capacity will indicate a low switching frequency of heated oxygen sensor 2. As oxygen storage capacity decreases, the heated oxygen sensor 2 switching frequency will increase.
When the frequency ratio of heated oxygen sensors 1 and 2 approaches a specified limit value, the three way catalyst malfunction is diagnosed.
Need more help?
P0421 MITSUBISHI CommentsHelp us improve AutoCodes.com. Leave a comment below or tell us if the information above help you fix the code. What are the symptoms on your vehicle for the P0421 Mitsubishi code? Have you replaced any parts?
Any information is appreciated. Thanks