I keep getting a code 25 and/or code 26 every once in a while. One coed is for air/fuel rich and the other is for air/fuel lean. It isn't on all the time, it just appears every once in a while and then goes off.

I had an O2 sensor replaced a while back as well as the AFM. The fact that it keeps going on and off makes me think it's got to be some kind of sensor, but I honestly don't know what the problem is.

I'm not about to take my 4runner into a shop and get screwed out of a ton of cash, but it's really starting to bother me and I want to get it fixed.

-Keith

 

I had this problem a couple of years ago. Check to see if all the vacuum lines are connected.