In a computer system an Interface is the combination of Electronics, Connecting Cable and Logic Protocol (software if you like) that permits one piece of the system to "talk" (transfer data) to another part.
Knowing virtually nothing about cars but having been involved with Computers since 1962 I suspect your car does not have an interface fault.
The fault light on the dash is either real (something has gone wrong) or imaginary (the computer only thinks something has gone wrong.
If the car's engine management computer is permanently illuminating the warning symbol when it should not be doing so then this may well be an "interface fault" which is stretching terminology a little - the circuit to illuminate the warning light has failed in the On state.
As to what to do - speak to a knowledgeable person in the garage and ask questions - ask what they mean by "interface fault" ask if the warning is real or imaginary - ask them what your realistic options are and the likely associated costs. Go to another garage and seek their opinion. Wait on here for a better and shorter answer.
Good luck...
Peccavi
June 2010
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