Dual O2 Sensors and how they work?

[EagleMark]

No misfires since I have owned it.

Injector spider was replaced along with intake gaskets, cap rotor plugs and a ton of other work about 6 months before I bought it. Total of recent receipts was $4000. and it also came with service records since new!

I just remembered when I got it I replaced 3 O2 sensors because I could not find records of them being changed and 3 is what the book showed.... taking a deeper look today there is one more post CAT O2 I did not change. This may be the issue?

Anyway to check CAT on vehicle?

[ony]

switch the o2s in the after cat position if the wires are long enough see if that bank has the same reading, if it has then the cat might have trouble. if it is a seperate duel ex. sys it may have one cylender running rich or lean.

[JeepsAndGuns]

Injector spider was replaced along with intake gaskets, cap rotor plugs and a ton of other work about 6 months before I bought it. Total of recent receipts was $4000. and it also came with service records since new!

Makes me wonder what was wrong with it to require all this work being done? Possiably the injector unit was bad or sticking on the side in question and therefore made the cat start going bad?

[EagleMark]

Makes me wonder what was wrong with it to require all this work being done? Possiably the injector unit was bad or sticking on the side in question and therefore made the cat start going bad?

Not really hard to get to that amount with GM dealer service, all service on truck was what GM recommened at milage for life of truck without regard to if it needed it. Main issue was Intake gaskets were changed, fairly normal with DeathCool anti freeze, full flush and green stuff. Spider injector while it was out, oil cooler lines, transmission cooler lines, AC high pressure line, spark plugs, cap rotor... new tires and some other stuff. This did not include the new transmission 1000 miles before that. Truck now has 116k.

As a follow up I installed the other post CAT O2 sensor I missed the first time and the issue is gone.

[1project2many]

I just remembered when I got it I replaced 3 O2 sensors because I could not find records of them being changed and 3 is what the book showed.... taking a deeper look today there is one more post CAT O2 I did not change. This may be the issue?

Failure to provide all information can lead to incorrect diagnosis. ;) Although I don't usually run into an issue with a lazy heated, post cat O2 without a matching code on the vans. Are the O2 heater codes enabled in that cal?

[EagleMark]

Yes all codes enabled. ALso passed the O2 test.

Fueling STFT and LTFT are now balenced/same bank 1 and bank 2.

What the dissasembly says is post CAT O2 has high low adjusting of fueling of -74 mv to +74 mv.

[JP86SS]

To clarify this for me...
Sensor 1 is the Pre-Cat sensor
Sensor 2 is post-Cat sensor
Bank 1 = cylinders 1,3,5, & 7
Bank 2 = cylinders 2,4,6 & 8
That's the only way it seems to make sense to me but I'd like confirmation of that.
Yes?

[EagleMark]

Cylinders 1, 3, 5, 7
Bank 1 Sensor 1 - Driver's side, before catalytic converter
Bank 1 Sensor 2 - Driver's side, after catalytic converter

Cylinder 2, 4, 6, 8
Bank 2 Sensor 1 - Passenger side, before catalytic converter
Bank 2 Sensor 2 - Passenger side, after catalytic converter

I beleive all vehicles banks are the same. But cylinders are not. Lots of internet reference to bank 1 always being on side with cylinder number 1 is incorrect. Like Ford cylinder 1 is opisite chevy number 1 cylinder. But banks are same.