Ls400 Mk 3 Oxygen Sensors

[Colin M]

Can anyone advise me whether there are 2 or 4 oxygen sensors on the Mk 3?

I have recently had a gas service and apparently the offside oxygen sensor is not working. I had a look at a PDF manual that I have, which is actually for a Mk 4, and there are 2 oxygen sensors for each bank of cylinders I.e. 4 in total. Is this the case for the Mk 3 as well, or are there only 2, one for each bank of cylinders?

Looking at the diagrams in the manual, I can see that there is a sensor on each of the 2 exhaust pipes but it is not clear to me where the other 2 sensors are located.

Any help would be much appreciated.

Thanks a lot.

[ColinBarber]

it has 4. Two before the main cat on the downpipes which are used to adjust the air/fuel ratio and two after the main cats which are used to check the cat is operating correctly.

[Colin M]

Thanks, Colin, that's very helpful.

I think the one that is not functioning will be the one that is before the cat, if this regulates the fuel/air ratio, but I will check with Toby Mackay who did the gas service and diagnosed the fault.