Toyota 4runner codes P0171 and P0420

Dear fellow Car Talkers;

Thank you for reading this and any reply you could give me.

I worked on my sister’s truck this weekend (2000 Toyota 4runner sr5 auto 135k miles California emissions 3.4L V6). MAF was trowing codes P0171 and there was also code P0420. Here is some of the data from the freeze data:

Frame 1 Mod#1


rpm: 2140



intake temp=51F


fuel system 1=CLSD

fuel system 2=n/a

short term fuel trim1=0.7%

long term fuel trim1=37.5%

short term fuel trim2=-100.6%

long term fuel trim2=-100.6%

I cleanup the MAF, truck passed NJ inspection,but light came back after leaving inspection station. I failed to clean the two wires completely inside the MAF. The two wires were still covered by dirt and now are clean as silver (I used CRC MAF cleaner).

PCV was old and stuck open, intake was covered by crude. Air filter was clogged.

I cleaned up the intake and truck run much better. But after 40 miles, the light came back again, with code P0420. The Ox sensor and A/F sensors were replaced around 2 years ago. The dealer wants to replace the catalytic converters. Thank you for any reply, sorry for too long post.