The oxy sensor usually throws a code and the idle is rougher and car uses more fuel than usual. Expect them to fail only after about 80,000klm or more
your talking about a failed 02 sensor that will produce an error code, do they just fail though or slowly go bad? just asking. I am sure my issue is either the accelerator pedal or the throttle actuator motor/mechanism but i dont know what the operating tolerances are for these things without a factory workshop manual to get that data from, I can see i will have to take it to the dealer and just ***** and moan until they fix it.