W168 A160 engine diagnosis warning light
 

Hi,
my wife's A160 has an engine diagnosis warning light appearing on the instrument cluster. We recently had the car serviced and the mechanic could not find anything unusual with the car and could not re-set the warning light.
He says that the most probable cause was the air mass flow sensor but as its an integral part of the engine computer, replacement cost from Mercedes Benz was AUD$2350. I am not keen on paying this amount and am looking for a lower cost solution.
The car has only travelled 80,000km. Has anyone experienced this before?
I would appreciate your suggestions and comments.
Regards,
Tassie Tiger