Do I assume correctly that you put the G2P in the fuel?I would put a strong cleaner such as G2P (guaranteed to pass) which can clean into the exhaust manifold before dropping $ on new parts. I use it every few mo to keep my cat/02 clean
Hi Davmac and others,Are you just trying to pass an emissions test - or trying to understand what repair is needed to remove the P0421 code?
Either way the guaranteed to pass stuff is worth a try - if only because it is a cheap try and as it is burned with your fuel it does travel through the cat.
Don't mess with the intake valve cleaning unless you are getting misfire codes and really poor running engine. If the valves have excess carbon they will either not seal or reduce intake air to the point of misfire. Carbon build up on the valves will not impact the catalytic converter or cause the P0421 code.
The P0421 code is a catalytic converter is failing code. It is one of only a few diagnostic codes that points directly to the source of the problem. It has nothing to do with spark plugs, MAF, etc. A tune up can help reduce tailpipe emissions, but won't fix this code. Don't read too much into the "warm-up" portion of the code. The real message is the catalytic converter is not doing its job of cleaning your exhaust of unburned hydrocarbons (think "fuel"). How does the ECM know? It monitors the oxygen sensor before and after the catalytic converter. If the downstream sensor is a mimic of the front sensor the ECM concludes that the catalytic converter is not doing its job. Since the ECM depends on the O2 sensors some people figure new O2 sensors might solve the problem. But, you have no O2 sensor codes (or any other codes) so changing the sensors is a long shot. Why did the catalytic converter fail at less than 100K? That is hard to say, but pouring raw fuel into the exhaust can ruin the catalyst. This can happen when an injector is stuck open, or the engine is run for a long time with a hard misfire due to failed ignition coil.
Absolutely. Cat converters ARE covered under the emissions warranty.Could the catalytic converter be replaced under emission systems warranty which runs considerably longer than standard warranty.I remember something like 8 years and 80,000 miles.Maybe it qualifies for free replacement.
I hear ya about the pollen and whatever else is in the air. I change my air filter every 20,000 miles and notice a slight improvement every time, same as in the past with previous cars. Nothing scientific but it seems to be a correlation with engine displacement. The CX-5 and the GM 3800 V6 filters are about the same size. The Mazda 2.5L is 2/3 the displacement of the 3800 (3.8L) and I change the filter roughly 2/3 as often (20K vs 12-14 K on the 3800). Then again, maybe I've just invented another automotive myth.Had the same fault recently. Cleared it two-three time but it came back on. The engine felt lazy, lack of power, slow acceleration. Possible fix, the diagnostic said, reprogram the PCM. I did not want to give in and spend the money for that so I kept looking for some other cheaper ways to fix the problem or make it go away. The idea being, start with the cheapest thing and go progressively. And then it dawned on me: 02 sensor, the car thinks that it doesn't get enough oxygen, right? How about the engine air filter! I live in a metro area where we just had the pollen season and I was thinking that maybe I could/should replace it. Replaced the air filter and the car seems happy again, engine power is back, acceleration normal. Drove it for two days now, like I stole it, with no problems.