P0160 O2 sensor, leaking coolant 2002 GMC Sierra

[new2meGMC]

First, I noticed the engine light came on, got my brother to check with his code reader and found P0160 O2 sensor fault, just after that the low coolant indicator came up in the dash. At first glance, I can't seem to see any apparent leaks. So I have topped up my coolant level once again. Checked dipstick, oil seems as new as I put it in a couple weeks ago! Any ideas as to what might be happening?

[txab]

P0160 O2 Sensor Circuit No Activity Detected (Bank 2 Sensor 2)

[gmtech4]

you have to get a light and look EVERYWHERE real close for the leak/staining to find the leak,

 

and throw an o2 sensor at it