rear oxygen sensor

[Leon Bezuidenhout]

Does the engine management system use the front or rear oxygen sensor to adjust the air/fuel mixture? What will happen if the front sensors where replaced, but rear ones give fault - does system go to default values or does this only happen when front sensor malfunctions?

Im going to remove my cat convertors. How will this affect the management system seeing that the front and rear sensor should see the same oxygen reading?

 

[TheFuzz]

Each sensor is monitored individually by the ECM. If one fails, the OBDII system will tell you exactly which one has gone bad by throwing a code. Replacing them individually has no effect on the others. Traditionally, the front sensors are first to go because they are closer to the engine, and have to sustain much higher temperatures.

Why are you going to remove your cats? There is literally no performance gain to be had by doing that, and you're just putting more crap out the back of your tailpipe that will soot up your bumper...

 

[OregonLC]

The fronts are for fuel trim and the rears tattle on you if you remove the Cats. In essence, they just verify that the converters are doing their job and reward you with a CEL if something is amok. It may also do something funky to your mixture/mileage... or it may not. Don't know of anyone that's done it on the LC.

Here's a good link on fuel trim: http://www.autoshop101.com/forms/h44.pdf

 

[Gunney]

Remember that SA trucks where only OBDII compliant after 2007. not sure if that makes a difference?

 

[marshotel]

I think LC Oregon is correct:

Only the front oxygen sensors provide feedback for air/fuel mix.
The rear oxygen sensors just tell if emissions are out of spec.

If the cats are functioning properly, there should be very little oxygen in the post-cat exhaust, so the signal from the rear oxygen sensors would not be very useful for AFR control feedback.

The question is whether the computer is programmed to go to default values if the emissions equipment is disabled.
I cannot think of a reason why this would be the case. But I am not 100% sure.

This is worth reading:
https://sites.google.com/site/mikefocke2/oxygensensors

Let us know what you find out.

I think you are wise to get rid of the catalytic converters.
They are a fire hazard.