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1999 Avalon air-fuel sensor problems

08-09-2006, 06:32 PM
In April 2005 the 'check engine' light came on, and the dealer diagnosed the problem as the air-fuel sensor; the bill was $465. The car had only 21K miles on it.

Just now (August 2006) the light came on again, with 35K miles on the Avalon. I took it to Advance Auto, who will read the codes for free. The codes were P1153 and P1155, both 'fuel air metering'.

The replaced part is out of warranty (12 months), and I can't afford to replace the sensor every year and a half. The strange thing is that the car has run fine both times, not even a drop in MPG. So why do I even need it?

Can anybody offer any suggestions? I need to fix it in order to get an inspection sticker this month. I can't do the work myself.

I think also that there might be two AF sensors in the Avalon. When I was waiting at the dealership the first time, another driver was talking to the service manager, and the guy was telling him this time it's the OTHER AF sensor that went. I was thinking, what's up, is this dealer charging everyone who comes in $500 for a new AF sensor or what?

The guy at Advance Auto said the new fuel with more ethanol may be causing some problems with these sensors, but I don't know why they should fail. Maybe it's just urban legend.

Thanks to anyone who can help.

08-15-2006, 06:09 PM
What are the exact codes you are getting? If it's something like P0171 = O2 sensor bank 1 sensor 1 lean, 99% of the time this does not mean the sensor is bad. This means something is leaning out the air/fuel ratio for that cylinder bank. I would start by removing and cleaning the MAF sensor.


08-15-2006, 08:25 PM
Hi Joel,

Thanks for replying. The codes are just as I said in my post: 'P1153 fuel air metering', and 'P1155 fuel air metering'. That's all the code reader from Advance Auto could give me.

Maybe a different reader could give me more info, but what can I expect for nothing?

At any rate, I have to get it fixed by the end of the month. I was late getting an inspection one year, and I got a surcharge form a ticket that lasted about six years. That wasn't funny.

08-15-2006, 09:05 PM
P1153 = Oxygen sensor circuit Response.

P1155 = Oxygen sensor heater circuit.

I'm not 100%, but I think these manufacturer specific codes refer to the bank #2 O2 sensor. The O2 sensor you can see threaded into the exhaust manifold on the radiator side of the engine. (bank 1 is on the other side) No response and no heater means the wiring or connector is broken or the sensor itself is shot.


08-16-2006, 05:31 PM
Hi Joel,

Thanks for the very useful extra information. I'll look into it ASAP and see what I can find. Hopefully it's just the electrical connection, not the sensor itself.

By the way, I talked with a service tech at the Toyota dealership before I read your latest post, and he said I had to wait several days and put some real mileage on the car after the repair before I went for an inspection sticker. According to him, the state's vehicle inpection computer system can tell when a repair was made, and for some reason will not approve an inspection right after the sensor is replaced. Seems very strange, and very creepy, like Big Brother is watching me.


08-16-2006, 05:38 PM
...According to him, the state's vehicle inpection computer system can tell when a repair was made, and for some reason will not approve an inspection right after the sensor is replaced. Seems very strange, and very creepy, like Big Brother is watching me.


That is correct. If the engine control module is reset, or a battery terminal is disconnected to reset the computer, your car will run in open loop mode for ~50mi of driving. States that mandate the emissions testing (computer scan) cannot pass a vehicle running in open loop. I had this happen on my 2002 isuzu rodeo. I changed out an oxygen sensor due to a blown heater, reset the computer then dropped the truck off for inspection. They had to drive it around for 2 days to get the computer to go back into full computer control! (closed loop).


03-04-2007, 03:47 PM
I thought I should post a belated reply to this post.

It turned out that the other A/F sensor had to be replaced, or so they said at the dealership anyway.

The first sensor that failed was part number 89467-41021 at $264, total charge $465.

The second sensor was part number 89467-41011 at $242, total charge $422. The car had 37K miles on it. I had to get it done to pass inspection, so what can you do?

The Toyota service department also said that the engine might not run right without the sensor, too lean and might overheat as I recall, but I can't be 100% sure what he said at this late date.

I have heard that the Avalon tends to have this problem with AF sensors.

Thanks to rodeo02 for his posts on this thread. :)

03-05-2007, 10:21 AM
The part numbers you gave are for a California emission spec Avalon and will be higher priced than the Federal emission spec Avalon. It is not a common problem, but to be expected around 100,000 miles as sensor efficiency degrades. It's unusual for a Cal spec car to be sold in Boston.

03-05-2007, 12:45 PM
It's unusual for a Cal spec car to be sold in Boston.

Thanks for your reply.

I don't know about that. I was told my a friend of a friend who actually works for the Massachusetts RMV checking out stations that do emissions tests that (if I remember it right) Mass. vehicles have to have the same emissions equipment as California's vehicles. He has a couple of Toyotas of his own, and is very happy with them. He can do all or almost all of his own maintenance on them, which of course is a big plus.

I bought the vehicle new from a Boston dealer, who got it on transfer from another local dealer. It only showed something like 6 miles on it, so I doubt it was a true California vehicle in the sense that it was shipped from there, but who knows.

It just bums me out that both sensors failed before I logged 40K miles. Granted that it's a '99 and I don't drive it that much, but even so. Expensive too.

Somebody also said something about maybe too much water in the gas tank from not keeping it full, but hell, gasoline now has up to 10% ethanol, which is one form of drygas, and besides, the products of combustion are CO2 and water, probably more than there would be in the gas. I don't necessarily give that theory much credence. I'm not a hard driver either - just the opposite.

Anyone with thoughts, please put your two cents in.

Brian R.
03-09-2007, 04:51 PM
Can't be water. Water injection is fairly common and poses no threat to sensors. More likely some other form of contamination or faulty sensors from the factory.

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