Check engine light - Diag codes...

[ericsbracer]

I've got a 99 Elantra GLS with the check engine light on. The car has over 90,000 miles on it, runs great, passed smog (California car) with flying colors a few months ago and the mileage hasn't fluctuated much in over a year.

My little code reader tells me I've got a P1613=Manufacturer Control Auxilliary Inputs - Auxilliary Outputs and then a P0136=O2 Sensor Circuit Malfunction - Bank 1 Sensor 2

Am I safe in assuming I've got a bad O2 sensor?

Thank You!