Hi, I have a 2005 mazda RX8 with 80k miles on it. I recently received the common p0442 and p0442pd code after a solid check engine light popped out.

the CEL came out of no reason. I didnt add gas within 14 days before that CEL popped. I drove the car to a local store, and it was fine by then. After I parked the car for 30min and restart the car, the CEL popped. I went to the parts store and get the code as p0442 and p0442 with a small p and d on side.

I searched and found out 99/100 people talk it;s the Evap system leak (However the store staff told me the diagnose of the OBDII is the O2 sensor)

I replaced with a new gas cap from local parts store. However the CEL is still there.

is the CEL supposed to turn off right after I replace the gas cap or will it take a few of on/off cycles? if it;s not the gas cap, what else could it be? I didnt see any visible leak from the bottom of the car. no funny smells. the car is actually running better than ever (maybe it;s the warm weather ). The store staff who checked the code said it;s the O2 sensor, is it non-sense or could that be the reason? Is there any need to send it to dealership to do a smoke test (where I hate to go)

any feedback will be greatly apprecated

 

The code will self clear after a few drive cycles IF (and only if) the problem was solved with the replacement gas cap.

Alternatively, clear the code yourself (or at the auto parts stores) and then give it a few days to see if it comes back.

 

So after I replaced the gas cap, I disconnected the battery and then the code didnt reappear until about 300-400 miles. And now the stable CEL will disappear by itself every time when the gas is low in tank (prob lesser than 1/2 or 1/3). However it will appear everytime after gas refill. So any suggestion?