The first
step in the process is reading the light code of the engine. The mechanic attaches a car diagnostic scanner with the car to know the trouble codes. These trouble codes indicate the faults in the car.
Mainly the information is contained in the OBD2 codes, and the mechanic has to interpret them correctly; for instance, the engine light code may indicate a fault with the car's exhaust. These codes are different for different constructs, makes and models of the cars.
Reading the AKA OBD2 code only takes minutes. After finding the error codes, the mechanic probes the vehicle further to determine the exact fault and resolves it accordingly.