I can only comment from a B18C 94 perspective. The second O2 sensor in the cat area is a check on the primary O2 sensor - the ecu compares the two readings and if there is too much difference it throws the check light. I don't know if the ecu reverts to preprogrammed maps in this case, but it certainly does if the primary o2 sensor is faulty. You just might be ok. Do a search in places like pgmfi.org