1997 350 ci code p0133

i have a 350ci 1/2 ton. i seems to run fine,I got a check engine light and my code reader say p0133 o2 sensor ckt slow response (bank 1 sensor 1)i used a actron cp9125 if this helps..can anybody tell me if the reader acurate or not? and shed some light to whats wrong.and if it is a o2 sensor which one..thanks for any input...jeff

Bank 1 sensor 1 is on the driver side, close to the engine in the "Y" pipe or exhaust manifold, and upstream of the catalytic converter. Provided there are no other DTC's present, slow response is usually a faulty sensor.

Thank you sir!!!!!!!!!!