Car Problem Reports
Audi S4 Check Engine Light Due to Vacuum Leaks, Oxygen Sensor, or Catalytic Converter Fault
Audi S4 Problem
Visitor, 2001 Audi S4, 149,000 mi
My check engine light hardly ever goes off. The problem from day one has been the oxygen sensors. I have had them replaced twice within the last three years and the problem has not gone away.