Does anyone know if there is a major difference between the front and rear O2 sensors - other then price. I need the rear one and the price is way more the the fronts.

 

I was under the impression that they are the same. but there is a sub-sensor which is on the cat, and that one is different.

 

They all look the same, but can they be interchanged?

 

ttt

 

No, they are different.

I'm can't confirm on a Lexus, but on other cars, one is a wide range, and the secondary are narrow range. The secondary ones are like a second opinion to make sure the primary O2 sensors are working w/in range.

Then there are differences between OBD-I and II

They can not be interchanged.

 

Are we talking about cars with three 02 sensors, or ones like my 92 that only have two? If they're like my 92 model, if one goes bad, you can just send (split) the signal from the working one to the other lead that goes to the dead one. One sensor is on the front exhaust manifold for the front three cylinders, the rear sensor is for the rear three cylinders. If the ECU receives an identical (split) signal from the working 02 sensor, it won't know the difference. There is no real functional reason for two 02 sensors on this car, IMHO. The only reason I can see is that if an injector plugs up, it can be easier to detect an out of balance a/f ratio from front to rear and spit out a code. It could *potentially* be used for fuel trim, but the stock ECU doesn't have the capacity to do per cylinder fuel metering, so that would be worthless.

 

Mine is a 92 SC400, so if I replace the defective rear one with a aftermarket universal sensor it should be OK? I can't buy a universal O2 for the rear only the front.

 

400's have 4 O2 sensors, 2 upstream, 2 downstream. They are not interchangeable, but do have aftermarket replacements at half the cost.

I'm not familiar w/ the 300's, but the the 400's have 2 O2 sensors per bank of cylinders.

 

Where can I buy the aftermarket rear O2's?