ShadowDrake

Been a while since I've been around here

Car has been fine for a long while but now I need to reach out for help. I've had P0135 and P0155 show up simultaneously. Can't get them to go away.

Quick basics: Rear O2's are unplugged and disabled in tune (heaters disabled, signal disabled, codes disabled). EGR is gone and disabled in tune. EVAP system still in place. Front left O2 has extension I made (soldered, shrinkwrap) which has been on the car for approximately 2 years. Front right is untouched.

Codes showed up driving into work one day - hadn't worked on the car for a while prior.

Checked fuse, looks okay (though after reading around more I'm going to replace it, I swear I checked it for continuity but hey, why not just replace)
Removed extension & checked continuity - all OK
+12V at sensor KOEO - though I don't remember which pins this was at - I can verify
Harness between firewall and engine over the bell housing is free, not pinched, and hasn't been pinched. I wiggled it and cleared the codes and they came right back

So, what to do... Car is still going into closed loop, signal seems to be just fine. Got some weirdness in AFR during tip in/tip out with ECT cold, but I still have been too lazy to finish perfecting the tune so it could be either.

I've reflashed my tune, though, this is via moates QH and not direct flash.

Where do I go from here? What's the easiest way to check the ground connections between the ECU and sensor?