I have an 01 yukon that had the codes p1133 & p1153. I installed 2 new sensors for b1 s1 and b2 s1. The 1153 code went away but the 1133 reappeared. So I took the new sensor back and got another one, installed and reset codes. Now both codes are back. I cleaned the mas and throttle body but the codes reappeared again. I don't think there is any exhaust leaks. Any ideas. Also checked for vacuum leaks and are ok.

poor connections or loose wires in the connector could cause that code too

Checked connections all is good

Just to be safe, you changed out the upstream sensors and not the down stream correct?

i would reseat the connections on the pcm too. aside from that i dont know. unless the brand of sensor doesnt play well with the gm pcm

Ok so I switched the downstream sensors and thought that worked but p1133 came back but p1153 is gone They are oem sensors