98 frontier 02 sensor

I keep getting code p0141, 02 heater sensor malfunction,bank 1, sensor#2. wich sensor is this front or rear? does anyone know how to check a 02 sensor with a volt/ohm meter. thanks in advance, dave

98 Frontier .. That should be the ka24 motor.. 4 cyl , thats the rear O2 sensor heater. I would start with the O2 sensor,, gl