Mercedes Benz fault finding

Engine light have started to come on intermittently. Asked Carnetics2 to replace anything that is faulty that is causing the light to be on. They had done an in depth investigation on critical parts and given a detail explanation of what they looked at and found no parts to replace. Want to congratulate them not saying parts need to be replaced just to start making profit. They have done all the investigations without any charge while giving a lift to Gautrein station and back. Car was fine expect the light till the day I sold it.