He is talking about the L and R brake lights on either side of the back hatch not working. And the R bumper light is out also.

If both the running light and stop lights are not working on the back, there are 2 circuits involved. And 5 bulbs I think in total.
If one of the bumper mounted lights is working, then that suggests (but not definitive) that the other 3 bulbs (L&R body, and R bumper-mounted light) are bad.
But each bulb has 2 elements inside (running and brake). So unlikely all 3 bulbs with all filaments went bad, unless you did not notice, and been driving around like that for months/years.

So he either has loose/corroded bulb sockets, broken wire, bad ground, bad fuse that looks good, etc. Or a transient voltage surge toasted both bulbs at the same time (less likely).

The OPs comment about bulbs going out when someone slams the back hatch tells me the bulb sockets are rotted out. Or the bulbs you are using are crap. So this H2 has issues.
You need to clean out every bulb socket on the back of your H2 and start from scratch.

Time to whip out the voltage meter and test those sockets with a helper stomping on the brakes.
Also, just to be sure, take a continuity tester to each bulb.

And I do not think this is related to the O2 sensor issue, if it even is O2 sensors.
If I recall correctly, O2 sensors can report as bad when you get the notorious H2 catalytic converter blockage (most commonly on the passenger side one).

 

Thank you everyone for all the help!

Admittedly, I screwed up.....I provided the wrong code, sorry! As it turns out, after testing again, the codes that come up are P0053, and P0135 (not 0153 as previously stated). I feel this might be better news though as it solely relates to just the bank 1 sensor 1 O2 sensor, no?

Ironically, the rear left brake light began working again, though the right side is out. So I'm thinking it's definitely a short somewhere, likely in the bulb housing. I'll be checking that later today.

So to recap, a brand new O2 sensor was installed on B1S2 and the two codes are still active, P0053, P0135.

 

 

whats the milage? if high mile then probably just bad bulbs and worn out O2 sensors. life span on a O2 heater is about 60k/100k miles

 

Are you using OEM or high quality sensors? The cheap ones often do not work good and the AC Delco stuff on Amazon is most likely a counterfeit part of dubious quality.

I buy most electrical parts right from my local GM dealer.

 

Incorrect sensor replacement!

 

Crap!!! I keep screwing up y'all my apologies....it was the bank 1, sensor 1 location and that's all that has been replaced! So the right location, right part, but still getting the same CEL codes!!

 

bank 1 would be drivers side.... was that the one replaced?

 

That's correct, it was the upper driver said sensor replaced. Bank 1, Sensor 1, but still showing the exact same codes as before... I'm breaking down and taking it to the shop to have them check it out later this afternoon since I have to get it inspected by next month. I'll definitely update once I get any answers as to what's causing it all.

 

**UPDATE**

Turns out the mechanic found a wire had been bent and was causing the CEL to come on...he didn't elaborate, but I've put miles on the Hummer and so far no CEL and it's driving great.. next issue is addressing the brake lights, but since I've had issues with them previously, I assume they're either blown or unhinged. Should be a simple fix I hope. I will update soon. Thanks again for all the help!!