The check engine light recently came on, I have a 2001 Sienna CE and Autozone did the free check the code was P1135. The print out shows 6 possible defects, all related to air/fuel sensors. Any ideas where to start?

It makes sense in many ways, but start at the cheapest/easiest solution 1st.

I am a service tech(in a different field than automobiles) and I can't count the times the problem a customer was having was due to the unit being unplugged!?!?

START CHEAP AND EASY and work your way up.:grinyes:

I just had my Sienna repaired for the same code. It was the Air/fuel sensor(not the oxygen sensor). Cost about $225.00 for the sensor and $200 for labor. Kind of expensive.