I have a 98 A4 Quattro 2.8 with an ongoing (electrical?) problem causing the codes for all four O2 sensor heaters to set (P1196-99). I've replaced both cats and all four O2 sensors recently, and this code is still being set. I tried swapping out the computer with another sourced from an identical A4; no luck. I live in California and need to get it to pass smog, which won't happen as long as the CEL is on. I've taken it in to four shops and no one has any clues as to what is causing these codes to set. Anyone encountered a similar situation and/or have any clue as to how to resolve it?