GM Truck Club Forum banner
1 - 5 of 5 Posts

·
Registered
Joined
·
3 Posts
Discussion Starter · #1 ·
Hi everyone
I'm new to posting on the forums so please take it easy on me.
I live in Georgia and have a 2004 suburban with a 5.3 flex 4x4. It has 315k miles.
It runs great and still gets good gas mileage. But I keep getting a P0157 code that I have spent months trying to fix.
When I first got the code I replaced the B2S2 O2 sensor and that worked for about 2 months then the code came back. I put my scanner on with the engine running and could see that B2S2 sensor wasn't switching like the other 3. I pulled that sensor and swapped it with B1S2 and had the same issue on the original location. With that I thought it must be a harness problem to the PCM. So I got a wire diagram and was able to confirm that I do have battery voltage when testing pins C and D and the pins A and B have continuity (not open) so the harness seem to be in good condition. I followed its routing and couldn't find any damaged areas.
I'm stumped on this problem and was hoping someone here has possibly dealt with this already. Any assistance will be greatly appreciated.
 

·
Registered
Joined
·
3 Posts
Discussion Starter · #3 ·
Just to ensure we are both in the same page, the B2S2 sensor is under the front passenger's feet.

Here is a list of possible causes, check the intake for leaks on the passenger side and check for broken bolts on the same side exhaust manifold.

Yes approximately. Passenger side after the cat.
I have checked for intake leaks but it won't hurt to do it again, I didn't think about the exhaust bolts. I'll look those over tomorrow. Thanks
 

·
Registered
Joined
·
3 Posts
Discussion Starter · #4 ·
RayVoy you nailed it. Took a look at my exhaust manifolds and have 1 broken bolt on the right side and 3 on the left.
I'm not looking forward to that job.
I checked the intake and it seems tight. I also checked short and long fuel trim and they seem good.
Thanks for the help!
 

·
Registered
Joined
·
15,685 Posts
Wade, yesterday I typed the post below and apparently didn't hit the post button.

An exhaust leak usually impacts the front sensors.
Let's return to what you've done.

You say, you changed the sensor and it worked for a few months.

To me, that says the problem is the sensor, or the wires at/near the sensor.
So the sensor could have failed; but you tried swapping it with the B1S2 sensor.
Did you leave the new sensor in the B1 side after the swap?

So let me add this today.
Broken bolts/studs are very common on the LS engines, this may not be the problem. Check my wiring comments above as well.

And a good test for the intake manifold is to use a propane torch. Just open the valve, don't light it, and play the gas along the gasket. If the engine speed changes, the gasket is leaking.

Anyway, let us know how you make out.
 
1 - 5 of 5 Posts
Top