xygen (Lambda) Sensor B1 S1: malfunction in circuit: P0130 - static - No indication on display -> 1.8T AUM

Let's get straight to the point, my brother and I are dealing with an electrical problem in my audi A3 1.8T 2003 it's the same engine as the MK4 1.8T, specifically on the Oxygen (Lambda) Sensor B1 S1: malfunction in circuit: P0130 - static - No indication on display.

We bought and changed the O2 sensor and it worked for one month and the code continued appearing (attached).

We also have checked all fuses, relays, and air leaks but nothing found.

Any ideas?

I would look for a broken wire on the harness going to the O2 Sensor. Easy for the stuff going to the exhaust to be cut/pinched when working on the exhaust system or installing/removing the engine.

I would check with Audi-centric online forums, or a knowledgeable local dealer/mechanic. They've probably seen that before, or can look up what the factory service manual recommends to troubleshoot that fault code.