I am going to replace my o2 sensors F+R. I found the front easy enought and i know the rear is before the catalytic converter but is the rear accessible with just lifting the car? or is it underneath something? My haynes book does not show a picture or describe its exact location.
No it is not before the cat. You found the "upstream" sensor, as in it is before the cat. Now you need to find the "downstream" sensor which is of course after the cat. Roughly within one foot past the cat. If you never got a code there is seldom a reason to replace it. If your engine is running in closed loop it should show a constant .5 volts.
Also... I replaced my 02 sensor on my '94SL1 last year due to some gas milage problems. My suggestion if you do have problems in the future is to get one out of a car at the wreckers. Save's big bucks if you are having problems and are not totally sure what the problem is. Local shop wanted ~$200 for a new o2. Got mine for $10. Turns out the o2 wasn't the problem anyways.
I went to autozone and they said the F+R were reading slow. Is the downstream as accessible as the upstream? I have an inspection and i don't want to the service engine light to be on. So i am going to replace them and hopefully the light goes out.
Can you give us the actual codes? Yes the car has to be raised to get the downstream. Autozone is more than willing to tell you sensors need replaced because they sell parts that way. The question is why. Dont go fixing "symtoms" without knowing the cause. For all we know you way over due for new spark plugs and wires. Or your engines all carboned up or burning oil like crazy. You arent giving us enough relevant info. I guess you arent worried about it.
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