1996 A4, 2.8. Replaced all four 02 sensors with universals. Had to cut the brown wire on the fronts to wire it right. The rears were 4-wire. All codes stayed clear for two months. Now I'm getting P1104 O2 Sensor Circuit (B1-S2) Voltage Too Low - Air Leak, and P0150 (B2-S1). Is the term air leak to be taken literally, as in a loose sensor? New cats installed along with a new coil pack within the last month. New plugs last fall. Cleaned the MAF around then, too. Only thing left is the plug wires and fuel filter (a huge PITA).

Any ideas why my new O2 sensors would fail so quickly? They are the cheap eBay universal type – I just could not afford four new Bosch sensors.