Hi,

I have a 2010 Mazda 5, and recently triggered code P0139 - O2 Sensor Circuit Slow Response (Bank 1, Sensor 2). I went and replaced it the O2 sensor after the catalytic converter and reseted the codes. After sometime the code came back again. The code comes and goes, but it stays most of the time on. I started using 93 octane gas, instead of 87, and the code has never come back unless I use 87 gas.

Any idea why this might be? the car should be able to use 87 with no problem. I thought about cleaning or replacing the MAF sensor just to see if it makes a difference. It could also the the catalytic converter, but I would prefer to be sure before spending $1,000 to replace it if it is not needed.

Thanks.

 

Bump. Im having the same issue.

 

check your spark plugs...

 

I fixed it by cleaning the mass air flow sensor and the throttle body air intake. Pretty easy take a look to youtube and the cleaners can be bought in Amazon or Autozone. Car runs also significantly better after.

 

^^^ Maybe but some people get lucky both with not damaging the MAS and perhaps eliminating the problem..


again check the spark plugs. there was a clue in the first post on this thread why I am repeating this!