MacBook Pro A1278 Late 2011Apple Hardware test dected an error 4NS/1/40000000:VDOR-19.769

AHT will throw a spurious voltage sensor error on some portables unless they are connected to power: Mac notebooks: Apple Hardware Test may report SNS alert when power adapter is not connected.

Those error codes not identical but similar ones will occur unless the power adapter is connected.

If that Mac's power adapter was not connected when running AHT, connect it and run AHT again.

That means there is a Voltage Sensor error.

You can try an SMC reset. Also make sure you are using an original Apple charger which is compatible with your laptop. Otherwise you may have a bad DC-In Board, or Logic Board, or Battery.

John Galt wrote:

AHT will throw a spurious voltage sensor error on some portables unless they are connected to power: Mac notebooks: Apple Hardware Test may report SNS alert when power adapter is not connected.

Thanks for mentioning and clarifying that detail for the OP. I should have specified that myself.