Occasional p0300, p0421, and p0431 codes
I have a 2004 Mazda 6s 3.0l v6 and I’ve previously addressed these codes by replacing both upstream o2 sensors, fuel pressure regulator, and pcv valve which DID make the check engine light go away but sometimes later on during driving it comes back usually with the p0421 code first. This vehicle has a slow oil leak and burns oil and I’m really hoping this isn’t the source of the ongoing issues..
Possible relevant parts that have been recently replaced:
- Cylinder 2 & 3 spark plugs and coils
- Bank 1 valve cover gasket (you might think this is leaking and causing the bank 1 code but I’m sure the leak is coming from the back/lower portion of the engine)
I’m a young hobby mechanic and would really rather to not tear open the engine because I don’t have the time/money/experience. Because the infrequency of the code/light its more of an annoyance (considering a minor part of the reason I got the car was for the power). I have a really basic OBD-ii tool and don’t mind getting more information!