2003 A4 3.0 6SPD.

I've had a bad O2 sensor on B2 for around a month. The other night I drove to a friends and I thought i heard a slight ticking noise, as if you had rocks in your tire. I parked everything was ok. I went to leave a couple hours later and my car started normal but instantly sounded like there was no oil, it was knocking so loud i just about **** myself. i shut it down checked the oil everything was good... I tried again the car MIL light was flashing at me. I have been nervous to start it up, i had it towed home. and haven't been able to look at it.. ill post the codes up. it anyone could please help me figure this out it would be greatly appreciated. Thank you

17528 - Oxygen (Lambda) Sensor Heating; B2 S1
P1120 - 004 - Open Circuit - MIL ON
16684 - Random/Multiple Cylinder Misfire Detected
P0300 - 001 - - MIL ON
16688 - Cylinder 4
P0304 - 001 - Misfire Detected - MIL ON
16689 - Cylinder 5
P0305 - 001 - Misfire Detected - MIL ON
16690 - Cylinder 6
P0306 - 001 - Misfire Detected - MIL ON
Readiness: 0110 1001

 

I'm leaning towards the cam chain tensioner on the driver's side based on the codes and the diesel sound...