oxygen sensor versus air fuel ratio sensor

[brant]

I'm getting a p0420 now that I've completed the flame trap service.
I realize I could have an air leak and tested all of the connections, and manifold mounting points with carb cleaner while the motor is running
unfortunately, I have not found a vacuum leak

so I'd like to test the 02 sensor next, and possibly replace one or both if I'm lucky enough for that to be the problem
at least Id like to rule that out before purchasing a new cat

I've heard that some cars use an air fuel ratio sensor instead of an 02 sensor before the cat
does anyone know what a 2001 NA v70 would use for a sensor

the output numbers are different for testing purposes, and I'd like to better interpret my numbers

my first sensor seems to be pretty much registering a .500 and sometimes goes up or down slightly but is not moving up and down as you would expect to see an 02 reading do. It will sometime vary between .475 to .505

however I've heard that the reading on an air fuel sensor should be steady and not constantly fluctuating
so if its an 02 sensor it is lazy, but if its an air fuel ratio sensor then that may be a good reading

does anyone know what the first sensor is on my car?

[brant]

my second sensor does move through the range, which I think is a bad sign in my case
I've heard that the 2nd sensor should be fairly consistent if a cat is working properly
how much fluctuation is there supposed to be at idle on the 2nd sensor?
thanks for all of the help

[jimmy57]

An oxygen sensor is an air fuel ratio sensor. Two names for the same thing. Oxygen sensors used to all be binary type and in late 90's (1999 for Volvo) the front sensors changed to a more sensitive wide band sensor but binary are still the ones used after the front catalyst.

Binary are read as voltage but wide band are not so easily read as their voltage output ranges within 15 millivolt span or less. Scan tools display wide band type as Lambda value which is normally .96 to 1.04. Lower is rich and higher is lean.

After 10 minutes running minimum, including some driving, the rear should be stable while idling and stable with steady throttle above idle. Usually .65 to .75 volts. If the rear ranges steadily with sweeps in less than 6 seconds +/- then that would be indicative of non functioning catalyst.

[brant]

actually they are not the same
the air fuel sensor operates at a much higher temperature and its output signal is inverse of an oxygen sensor
thus the reason I want to find out if Volvo was using these in 2001 as my first sensor output signal is not fluctuating the way you would expect an oxygen sensor to fluctuate.

the output signal of an air fuel sensor is more steady, but I'm trying to determine which type my car uses, or if my first sensor is bad/lazy

http://www.discountconverter.com/cataly ... -&News=248