Recurring bank 1 O2 sensor code

[ukrkoz]

About a month or bit more, my Tahoe threw MIL and pointed towards bank 1 sensor 1 low. I erased code, it came back about 2 weeks later.
Bought and installed Denso O2 sensor. Installed good, even little green tab locked in place.
Did this 2 week back Saturday.
Same code popped again today.
Unless bank 1 sensor 1 is not the precat on the driver side - I'm at loss.
What does it want else?

 

[wjburken]

About a month or bit more, my Tahoe threw MIL and pointed towards bank 1 sensor 1 low. I erased code, it came back about 2 weeks later.
Bought and installed Denso O2 sensor. Installed good, even little green tab locked in place.
Did this 2 week back Saturday.
Same code popped again today.
Unless bank 1 sensor 1 is not the precat on the driver side - I'm at loss.
What does it want else?

What is the code it is showing?

 

[ukrkoz]

Aaahhh.. had it erased....

 

[ukrkoz]

But I had it scanned and this is what O2 shows. Actually, I scanned all 4 of them, they all show same. So I figure, it's not sensor

 

[ukrkoz]

OK, codes are P0030 and P0135. Both B1S1
I ran live diagnostics several times and every time every O2 sensor checks out.
So it's not sensor.
Something else.
I know for granted that I have exhaust leak from the bank 1 exhaust manifold gasket. I did Chris Fix's trick with shop vac pumping air into the exhaust last year or so, and sprayed soapy water at that gasket and it bubbled quite well. So there's that. I just dread doing that gasket for 2 reasons - 1. fear breaking bolts and 2. there's that darn 3rd bolt on manifold flange, that is real hard to get to, even with lift. Plus, I didn't really have any issues with thta leak for quite some time. If that's the cause, of course.

 

[ukrkoz]

Just to make sure.
B1S1 is on the DRIVER side, right?

 

[j91z28d1]

is the leak from a broken manifold bolt or down at the collector flange?

 

[wjburken]

is the leak from a broken manifold bolt or down at the collector flange?

my guess, based on the “3rd bolt” comment is the collector flange, but I could be wrong.

 

[Fless]

Just to make sure.
B1S1 is on the DRIVER side, right?

Yes, driver's side, pre-cat.

 

[Fless]

But I had it scanned and this is what O2 shows. Actually, I scanned all 4 of them, they all show same. So I figure, it's not sensor

I'm not sure of the graph -- the mV value range may not be great enough to see the full high and low values, or the sensor might be moving just a little if that's all it does. The upstream sensors should move a lot up and down between 100 and 900 mV as they sense between lean and rich. If the value sits there around the 450 mV area and doesn't move much, it's not reacting.