Been a little while since I've been on the site. The CEL on my 4runner recently came on, and I've had a hard time troubleshooting the codes. I have a 25, 26, 43, and 51. Codes 25 and 26 I am assuming are caused by the same issue. So far, I have changed o2 sensor and swapped AFM with known good AFM. TPS has been replaced within the past year, so I'm assuming it is good. Recently changed plugs, wires, etc. Anything else that I'm missing?

 

OK, little update. I decided to check on the o2 sensor again and see if something was wrong with it. The wires seemed a little loose, so I fixed that and reset the computer. Now the 25, 26, and 43 are gone, but now I have a code 21 - o2 sensor deterioration and the code 51. The o2 sensor is only about 6 months old, so that doesn't sound right (and I didn't know this was a CA truck). Any ideas?