Technical System voltage

[notsmartcars]

I've had the following faults ,my blue tooth to the radio stopped working that didn't bother me and then although I could turn the radio up from the steering wheel I couldn't turn it down but that didn't bother me but now I have the engine and triangle light on which on the multi scan comes up as variable oil pump fault??? So now I'm Starting to try and find my way round my 13 plate 500 diesel
On my multiscan it shows with the engine running a max of 13.6 at the Ecu? But at the battery I get a max of 14v using my multimeter also with the engine running now with cars I've had before this would be too low to keep the battery in tiptop condition .. I actually bought a brand new battery a few months ago rather than wait for it to fail during the winter which went completely flat when the car was parked up and not run for 6days
When the weather warms up I'm going to check the output a the alternator looking for the missing volts as I've heard several times start with new battery which also means make sure the charge rate is correct
Am I alone with these faults ?

 

[swifty500]

Check all your earth straps and connections-voltage cant return the circuit if the earths are corroded or loose