Engine coolant sensor CEL
 

I've been getting a CEL for the coolant sensor in my '03 9-3 SE, so I replaced the sensor, but lo and behold, the CEL has come on again. In addition, the symptom that was occurring prior to replacing the sensor has returned. The temp gauge will go dead while driving, sometimes triggering the CEL and sometimes not.

For those out there that may say 'thermostat', I'm getting cabin heat without any problems, and the engine is running properly.

Could it be related to the ACC system? I read that it utilizes coolant temp as one of its inputs.

I also thought it may be a ground fault, but wouldn't that affect other systems connected to the same ground?

Thanks for any help.

Brian
This has me baffled.