I have a 2001 RAV4 with less than 30K mi on it. Since the car was 2 months old, it started to do weird things, like wouldn't start and the dealer claimed they couldn't find the cause for over 3 days. Then, it had codes 420, 430 with the MIL on. The dealer reset it. Now, literally weeks after the warranty expired, MIL comes on again, and dealer says it's yet another problem, code P1135. The dealer wants over $600 to fix the A/F sensor that he claims went out. I am bloody suspcious that I've been having all this MIL crap going on, thinking, there's a bigger underlying problem. Some of my mechanic friends further confused me, because they claim there are no separate O2 and A/F sensors, it's really just one. Since the O2 sensor would have been covered under warranty, it really makes a big difference to know what is going on. Does anyone know what really causes P1135 to register in a very low mileage car, and does anyone know the relationship between the O2 and A/F sensors in a 2001 RAV4? I forgot to mention, although I'm not sure if it's relevant: our gas mileage seems to be WAY down since the dealer "reset" the sensor after the 420/430 codes four months ago.