p1153 even with 2 OEM o2 sensors

[WeekenderNutJob]

2008 Yukon XL Denali, 6.2L AWD - P1153 (Bank 2 Sensor 1) code even after replacing the o2 sensor.

Replaced Sensors: About a year ago I replaced both the upstream and downstream sensors on that side with AC Delco ones of the same part numbers when it had codes, which worked well for about a year. Recently started getting just an upstream sensor error, p1153, so I replaced upstream again with OEM, cleared all codes, and ECM memory reset, however, I get codes again after the drive cycle. At this point, I am not convinced it's a sensor issue anymore as the OBD Reader shows that the sensor voltage is working similarly to Bank 1 sensor 1.

Smoke Test: The next assumption was an exhaust or vacuum leak, so I smoke-tested the exhaust from the front intake and from the back exhaust for a potential manifold or vacuum leak, but I did not find anything indicating a leak anywhere on a cold engine.

TSBs: As a side note there is a TSB (https://www.tsbsearch.com/GMC/08-06-04-045A) that talks about the need to reprogram ECU due to gas sulfur levels but I assume if it was an issue with the sensor and ECU reprogramming after an o2 sensor, then it would have been an issue when I replaced the upstream originally a year ago. I always run 91+ octane gas, from top-tier stations, per the manual.

Before I take it to the dealer, for more diagnostics, or ECU reprogramming, does anyone have further suggestions on tests I can do?

 

[WeekenderNutJob]

Hoping to bump this for any feedback. Still not able to isolate the issue. Here is what I have done more since the last post:

Connections: All clean and good.
Fuel pressure: About 60-65 psi key on but not running, and 42 when running which seemed somewhat low...but within the low range of "normal". Fuel pressure is maintained when the key is off and after 5 min.
Injector cleaner: I also am running some injector cleaner through it in case maybe it's a clogged injector on just that passenger side.
Coolant: No use of coolant to suggest a contaminated exhaust.
MAP Sensor: Cleaned recently.

 

[Fless]

Is the fuel system management going into closed loop and staying there?

I would be curious about the short- and long-term fuel trims (both banks) and what the MAF is reporting at hot idle, if you have access to that info.

 

[j91z28d1]

any chance you have an aftermarket airbox of some sort?

 

[WeekenderNutJob]

Is the fuel system management going into closed loop and staying there?

I would be curious about the short- and long-term fuel trims (both banks) and what the MAF is reporting at hot idle, if you have access to that info

any chance you have an aftermarket airbox of some sort?

Nope, bone stock.

Yes the fuel system management is going into closed loop and staying there. Short term and long term fuel trims are lower on bank 2 versus bank 1...but I don't know why. Should I pull the fuel injectors out and test them one by one? Or at least ohm out? My next test I think was going to be either a stethoscope on each injector, or a back pressure test on the catalytic converters.

 

[Fless]

Would still like to see the MAF reading in g/sec at hot idle, just to be sure it's close to engine displacement. And hearing that the fuel trims are lower on one bank than another doesn't really tell much. Where are they numbers-wise? Do the trims change a lot when raising the RPMs to 1500 or 2k?

The upstream sensors can be swapped side to side to see if the issue follows the move.

You can test the injectors without removing them by doing an injector balance test. You'd need a scanner that would do that, though.