Take it to the local repair place. AutoZone is in the business of selling parts (whether you need them or not), not correctly diagnosing and repairing cars.

I know AutoZone isn't in the business of repairing cars. I only took it there as my son said they could diagnose the problem of the engine light staying on. Whether they are correct with their diagnosis, there's another story, LOL. My DIL's engine light stayed on in her Honda and that's what was wrong with her car, so it must be a fairly common problem.

Does anyone know if my Avalon has more than one sensor? Should I not be driving it until I can get it fixed?

Check make sure your gas cap is on tight.I had that problem.I was told no one knows whats wrong.Keep checking finally heard on tv gas cap wasnt on tight.All that money spent.

Just last week, I bought a downstream oxygen sensor from NAPA for my wife's '97 Saturn Wagon. Cost was near $100 with tax for the sensor alone (not including installation and trouble code checks). There is 80,000 miles on this vehicle and the original sensor. Her auto has two oxygen sensors: One in the exhaust manifold, and one at the tail end of the catalytic convertor.

Many, maybe now all automakers use two sensors.
It is my idea that , on a scheduled service basis, that the sensors should be removed and cleaned ( every 5 to 7 years).
These were, at one time, scheduled for replacement every 50K miles or so.
Then that requirement was dropped in the era of 100K miles tune-ups..I do not know if I agree with this "nearly no-maintenance concept"...

That part wouldn't be made by Toyota anyway.

I think the reason that oxygen sensors were scheduled maintenance items is that the computers back then didn't have the capability to test the oxygen sensor for proper function.

Now, they do, and when the oxygen sensor isn't working right, they light the check engine light and store a code.

On a 4 cylinder engine, you will normally find 2 sensors, one upstream (before the cat) and one downstream, (after the cat).

On a "V" engine, 4, 6, 8, 10, or 12 cylinder you are going to find at least 4 sensors. Two upstream and two downstream. One of the advantages of this system is each half of the engine is controlled independently. This allows for not only better individual cylinder control, but it allows for the computer to have better learned values and detect when a problem is occuring.

There is one 4 cylinder in line engine that I can think of that has 2 up stream sensors, and one downstream for the same reason, better individual control.

BullD...

The idea of the gas cap being loose is one thing, and it will cause very specific trouble codes to be set. In fact Ford's actually monitor fuel levels, and if a Ford computer see's the fuel level increase such as a fill-up, and then the car fails it's evaporative monitor check the car will actually turn on a lamp that specifically says "check gas cap" before the check engine lamp ever comes on. As far as "no one knows whats wrong", thats false. A properlly trained and equipped technician can diagnose a loose cap, and would not have to guess if that is what is wrong. If the shop/tech you choose to use cannot do that, then you really have to ask yourself why are you choosing them to service your car!

Yea O2 sensors are rather difficult Just finished replacing the old one.

{{gwi:1406499}}


As you can see "Yea" of course theres alot of carbon build up which could explain why my car's Check Engine Light would go on and off every so often. Non the less not a everyday thing the light went on. Hopefully this solves that twitching and so far so good. Use Bosche there probably the most dependable brand when switching to a new O2 sensor