OBD fault N/A

[g4jnw]

I rarely use the car on a long run but did so last week, the engine warning light came on but nothing obvious. The following morning on switch on the light went out, a week later it came on again. I plugged my OBD reader in and it showed 3 codes but N/A so not sure why as N/A on searching google means manufacturers codes not compatible.

The only thing i find on the car, since buying it, is the fan constantly on. Its a 2010 Corsa D 

Anyone else had this?

[Vauxhall Owners Club]

Sounds like it could be a coolant temperature sensor that is failing or on the edge of its operating limits and causing the light to come on and the fans to stay running?