On my 2002 2.7l Santa Fe, I get a CEL after at least 1 hour highway driving indicating O2 sersors on both banks. Only happens on highway - I can drive for weeks in town and short highway trips. As such, I suspect something other than sensors as always both banks fail same time. Replced intake air filter on spec suspecting insuffecient air flow. Engine runs fine. What else can cause this thats cheaper than replacing up to 4 sensors first (engine code does not indicate which sensors other than bank 1 and 2)? Any ideas to research appreciated.
Thanks in advance