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.

 

[ukrkoz]

I'll go backward.
Yes, O2 sensor moves up and down when I ran live graph.
Yes, all sensors pass test on both Torque and smarter scanner
I am referring to the 3rd bolt on the manifold flange, next to cat, as it is crammed between the flange and the engine block, with very little room to get to it.
Exhaust leak is on the engine head side of the manifold. Apparently, leaking gasket. Now, this motor was out 2 yrs ago, as it was in shop, to have lifters replaced, and they broke head bolt and had to pull engine out to have it replaced. So I am safely presuming, they had exhaust manifolds removed for that? What I found later down the road, around spring last year, that those flange bolts were missing on both manifolds, so I fixed that. Engine was reeking of exhaust, standing next to it. That tripped me to scope exhaust and I found those missing bolts, well, holes for them.

 

[j91z28d1]

I'm going to say you fix all exhaust leaks first.

I don't know what kinda gaskets they used, but the oem are 3 layer steel and they can normally be tightened up without replacing.

 

[ukrkoz]

I know. Just dread the job.
Nuts are tight, I tried.
Really, don't want to snap a stud

 

[j91z28d1]

are any broken off? if it's leaking at broken bolts they have those clamps.

if all the bolts are good and it's leaking, yeah I'm guessing that shop used junk gaskets and you need new ones. but you might get lucky since it's been apart a few years ago, the bolts might come out without breaking

 

[ukrkoz]

Yeah, I'll just do it next weekend. Got lots of Liquid Wrench. Shouldn't be that hard.....

 

[ukrkoz]

I have a question then.
If manifold is held in place by simple bolts, do I really need to disconnect it from the exhaust pipe to replace only gasket? Won't it move away from the block enough to simply remove the old gasket and slide the new one in?

 

[donjetman]

go far it, but it may fight you getting it to line back up? Let us know please.

 

[j91z28d1]

I have a question then.
If manifold is held in place by simple bolts, do I really need to disconnect it from the exhaust pipe to replace only gasket? Won't it move away from the block enough to simply remove the old gasket and slide the new one in?

these are copper and I'd use oem 3 layer but notice the end bolt holes are slotted. if you can do that to the gaskets you have, you should be able to pry the manifold out a bit slip them down in.

as for getting the old ones out, leave one of the front or rear in, should be able to pull up the gasket, and then put say the front in, remove the back and pull it the rest of the way out.

I've not done this on one of these trucks, only an older small block chevy motor with more flexible headers. but might be worth a try.

 

[ukrkoz]

So I ran live scan on O2 sensor. It's reading just fine

 

[ukrkoz]

Have AC Delco gasket ordered. Next Saturday will be the D day. Will report back