My battery gauge goes to low and check gauge light comes on when driving truck. When I turn off and then back on gauge goes to middle, Last time it happened left truck running check battery voltage 14 volts checked from alternator also 14 volts, gauge still reading low, turned truck off battery 12.6 volts. I have driven it about 15 miles after it went to low and truck runs fine. Also no error codes. Any advice would be greatly appreciated.