Causes and Fixes P0421 Code: Warm Up Catalyst Efficiency Below Threshold (Bank 1)
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- เผยแพร่เมื่อ 27 ส.ค. 2024
- How To Fix P0421 Code: Warm Up Catalyst Efficiency Below Threshold (Bank 1)
A P0421 Code is set when the catalytic converter falls below 95 percent efficiency.
How To Test Oxygen Sensor Heater Element Video:
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Possible Causes of a P0421 Code:
Failed A/F Oxygen Sensor
Wiring (Open or Short)
Exhaust Leak
Faulty Catalytic Converter
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Thanks for the info 👍🙂
I have really bad spark knock or pre detonation and I ran codes yesterday and got P0421 could this be the cause?
It needs to be diagnosed, but if the catalytic converter is clogged up, it can cause issues.
I have a 2002 mazda 626 4 cyl, the p0421 code came up & said "...bank 1 catalyst system below efficiency..."
Is this the cat?
Wow❤❤❤❤❤
I have an 06 mx5-Miata and I bought used performance (catted) headers which were fine the day of install but got the p0421 very next day. I cleared it and continued driving with no code that day but decided to scan and saw that I actually had the code but in pending state. I am almost certain the code will eventually be back but this video is going to be a lot of help. I bought some Cataclean which I will try along with a nice long highway drive in hopes of cleaning some deposits.. if that doesn’t do it I have a desperate attempt of using a spacer for the second O2 sensor as some have suggested for my situation(non Fowler method). I really really do not want to find out I bought a broken set of catted headers so after attempting those solutions I am going to monitor temps with a temp gun as you mentioned in the video. Is this a guaranteed method of diagnosing a bad cat? If it is hotter upstream than downstream does that mean the cat needs to be replaced or is it simply a matter of cleaning out contaminants that may be blocking airflow upstream?
It is common to diagnose a clogged CAT by temperature, but more tests can be done. Since the headers are aftermarket, it may be best to see what results others have had in the forums or Reddit and if they had any issues.
@@HVAC_Mechanic Thank you for the response, if there are any specific tests I can run please do let me know. The p0421 is the only code and others in the forums mention that it is common for 'performance' headers to throw this code due to the fact that it is much less restrictive than OEM. This is why some mention that a spacer for the downstream O2 sensor can help by moving the sensor's location away from where all the exhaust gases get concentrated in the middle. The weird thing is that this is a solution for an opposite situation than that of a clogged cat converter. So I guess I need to figure out if these used 'performance' headers are letting too much air pass without being catalyzed, or is it the opposite and not enough air is passing through because its clogged? 🤷♂
I've got a Mazda 3 2005. I'm getting p2004 which means the intake solenoid has failed and the intake is stuck open. and I've confirmed the solenoid is dead. I'm also getting the p0421 code and wondering if the intake value that is stuck open is causing or can cause the p0421 code to come up.
Yes, if the engine is not running correctly and fuel is dumped into the exhaust, it can clog up the CAT and cause a P0421 code.
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