So I bought a 1994 Camry XLE V6 with 88k miles and the check engine light came on after I bought it. One Hundred dollars later the dealer tells me I need a new O2 sensor and they'd put it in for $480. I told them that was crazy. The maintaince invoice says "Found Code P0135- Vehicle needs new O2 Sensor, Bank One Sensor One. So I should be good if I buy a new sensor and have it installed right? What worries me is that in the maintaince records there is an invoice that says the "front bank O2 sensor" was replaced, is this the sensor? Should the sensor really be going bad after only 40k miles?
It is not unheard of for O2 sensor to go bad after 40K miles, especially on a car not driven a lot (like yours). Age is more important than miles.
To get it replaced cheaper, you could try an independent garage that specializes in Toyota, or try another dealer. But if they are charging you $100 for the diagnosis, then you are getting ripped off and I would complain to Toyota, the Management of the dealer, and my local TV station consumer reporter. Changing these yourself is not as easy as it may seem, and may require a special tool.
You should get this fixed, because the O2 sensor adjusts the fuel mixture and you may be running too rich or too lean without it functioning properly.
BTW, if the light came on within a week of purchasing the car, then it is likely the previous owner knew about the problem and just reset the computer (pulling the computer fuse). When the computer is reset, it usually takes several days for the light to come back on for some of the bad O2 sensors (that is how it worked on my 92 V6 Camry).
Bank 1 is the rear bank on your engine, not the front. Your records indicate that bank 2 has been replaced. Bank 1 is in the rear exhaust manifold (close to the firewall)and is accessed from the bottom of the car.
On the V engines, there are two O2 sensors upstream of the cat (bank1 sensor 1 and bank2 sensor 1). The one that wasn't replaced 40K ago has now gone south.
sparkplugs.com has some decent prices on Denso and NGK O2 sensors if you want to DIY.
Another bit of advice if you are planning to pop it in yourself: grab a can of penetrating fluid and let that old sensor marinate for awhile - like overnight. I find those older Toyotas - especially the rear bank - will often have threads in the manifold that are seized. Figuring out a way to get a tap in that rear bank while it is in the car can be a real headache. Let the old threads soak for a while and you shouldn't have a problem getting that sucker out.
The next time the MIL light comes on, go to Autozone to have them read the code(s) for free. Or buy a simple OTC OBD-II code reader for $69+tax at Pep Boys, Advance Autos, Checkers, or Kragens. It's cheaper than the $100 one-time deal at the "dealer".
$88 is a good price for an oxygen sensor. Except I don't think the Denso thimble type oxygen sensors are very good at all. I'd go with the new generation of Bosch planar oxygen sensors. These are the ones with vent holes only at the tip of the sensor instead of on the side of the cap on thimble types. Lights up faster, uses less power for the heater, and is more difficult to contaminate than the old thimble type (which will gradually be phased out as EPA requires lower exhaust emissions.)
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Denso sensors may be the source of your problem, but you do have to make sure there isn't something else upstream that causes the oxygen sensor to go bad, otherwise your new sensor will go bad as well. Things like internal coolant leak (V6 does that with their flimsy head gaskets), rich mixture, internal oil leaks are some of the causes. But these should not affect the heater circuit, which the P0135 code was about.
Note: P0135 refers to the heater circuit of the rear bank or right-hand bank sensor. Can you measure the resistence of the heater circuit from your old sensor?
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