Why do 2500's only have (2) O2 sensors

[Todd Edge]

My '02 has an O2 sensor before each catalytic converter but, none after the cats.  I always thought OBD required 1 O2 sensor before the cat and one after the cat.

Todd

[MS03 2500]

Be glad it does not have them, you must have a early model 02 AV.

[Todd Edge]

I guess so.  My catalytic converters are clogged, after 111K miles.  Rather than replace, I'm going to hollow them out and if it is too loud, I'll replace with some high flow units.  I guess with no after-cat sensors, I won't trip the check engine light or anything like that.

Thanks,
Todd

[ItsStopher]

My info shows 2 before and 2 after  Are you the original owner?

[MS03 2500]

Some early AVs 2500 did not have them.

[Todd Edge]

No, 2nd owner.  I have all the receipts for all work done on it and there is no mention of any exhaust work other than adding a magnaflow muffler.  I checked al lthe wiring under the truck and have no leads for any additional O2 sensors.  The check engine light is not on either.  I'm a bit baffled but, don't see any signs that it ever came with the 2nd set of O2's.

Todd

[MS03 2500]

Do you have a cables to your throttle body.

[MyBigToy]

It's not a big deal - all the rear O2 sensors do is look at the efficiency of the catalytic converters. It's just one more expense to have to maintain so count yourself lucky.

[MS03 2500]

It's not a big deal - all the rear O2 sensors do is look at the efficiency of the catalytic converters. It's just one more expense to have to maintain so count yourself lucky.

X2 

[Todd Edge]

Thanks for the information!

[ramv]

Yep, the front O2 sensors control the FI, the rear just trigger CEL.

[Eskimo]

My '01 2500HD with the 8.1 didn't have any post-cat sensors, I assumed it was because trucks over a certain GVW didn't need to meet certain federal emmissions requirements back then...