O2 sensor P0130

Check engine light came on yesterday and the code that came up P0130 AU (o2 sensor, bank A, up stream from the cat.). I just replaced all four of the O2 sensors with R.N. sensors six months ago. Any reason this code would be triggered? Possibilities include, bad o2 sensor, short in wiring, moisture in connecter, ... Any experience or thoughts? I did spray the engine bay out a few days prior to the light triggering and that is what I also did when I had multiple failures of the sensors six months ago. Seems odd a bit of water would muck up the connectors.

Land Rovers are not waterproof, you'd think the Brits would have all the opportunity in the world to develop a submarine-like car, but no. Most electrical problems are because of: bad grounds, bad plugs, bad wire. Try using Dielectric Grease in all your plugs, thus sealing out water. And quit worrying about having warning lights on, most folks don't pay any attention to these, if the vehicle seems to be running right. The lights come on, the lights go off, whenever they feel like it. Also the Brits have no concept of how to make plastics suitable for automotive use, it's all brittle. And the wire they use is rubbish, if it's oxidized near the connector, it's probably oxidized to the opposite end.

'95 R.R.C. Lwb (Gone...)
'76 Series III Hybrid 109
'70 Rover 3500S