Toyota Repair: check engine light on 99 avalon, auto parts store, voltage meters

Question
Hi Andrew,
My check engine light comes and the car runs very rough, bucks and
hesitates.  Either of these can proceed the other.  It may continue for a day
then stop.  I thought I had the error code, but can't find it.  It indicated that
the front bank was running lean.  One of the reps at the Auto parts store
thought it was likely the front O2 sensor, but since it was a couple hundred
dollars I thought I'd do a little more research.
Thanks for you help,
Gary

Answer
Well, if it is the O2 sensor, it can be simply tested. That's why we have voltage meters, it cuts out the guess work. That's why the Auto Parts individual is exactly that...he sells parts. He's not a technician.

If you check engine light is still illuminated, open the check connector (located on the passenger side under the hood). It should be a little black or gray connector with a flip up door. with the ignition key in the 'on' position, connect a wire to the "TE-1 to E1" connections. The light will start to blink a code.

Once this is done, come back and tell me what the code is.

Thanks