2001 Prius, 210k+ miles. Last week we got 3 codes: - Mass Air Flow: P3191 - Misfire: P0300 - Catalytic: P0420 I removed the MAF sensor and cleaned it with a special MAF cleaner. Then reseted the codes. Today, P0420 came back. What's next? - spark plugs - PCV - air filter Should I change the downstream O2 sensor too?
How does the car run? If the misfire is gone and the car runs good the pcv and air filter may just be a good cheap need to do anyway. Plugs are also easy to check so I would pulI one and check it's health. Iridium plugs last a long time. I had a P0420 that would come on intermittently for about 6 months in my 2002. The car ran great and was not burning oil so I figured it was not the catalytic converter. I then replaced my up stream O2 sensor and put the anti-fowlers on the rear O2 sensor. Both simple cheap fixes. The up stream is just a bit difficult to get to. Code never came back and I am not sure which one fixed it. If you are not burning lots of oil, I would try the O2 sensor and the anti fowlers. TomK
It is a spark plug anti fouler. There are threads on how to do this as one needs to be drilled out and the two are put together to set the sensor further away from the exhaust gases. I spelled it wrong originally. I think this is the set I bought. TomK
