Volkswagen vehicles built after 1996 are equipped with a system of sensors known as On Board Diagnostics (OBD II). These sensors monitor many vital engine functions and help to lower harmful emissions. When one of these sensors fails it sends a signal to the engine computer to illuminate the "Check Engine" light in the dash. To clear this light you will need a diagnostic code scanner. Scanners range in price from £26 to £78 and are available at most auto parts stores.
Connect the diagnostic code scanner to the vehicle's diagnostic port. The port will be located in the dash below the heater controls.
Turn the key to the "Run" position, but do not start the engine.
Press the button on the scanner that reads "Scan for trouble codes."
Wait for the scanner to finish scanning the engine's computer.
Press the button on the scanner labelled "Clear all trouble codes."
Disconnect the diagnostic code scanner from the vehicle.
Be careful when inserting the diagnostic code scanner into the diagnostic port on the vehicle. The small pins on the scanner cable can be bent. If you do not own a diagnostic code scanner and do not wish to purchase one, most auto parts stores will read and clear troubled codes at no cost.
Clearing the troubled codes from the engine computer will not solve the underlying problem that caused the Check Engine light to illuminate. If you do not fix the underlying problem, the Check Engine light will come on again.