When performing this function the car will automatically rev up the engine several times during approx. 20-40 seconds to decide how good the cylinders are relative to each other. The best cylinders receive the value 100%.
There may not be any permanent fault codes for components that affect the following:
Coolant temperature sensor.
Crankshaft signal.
Camshaft signal.
Vehicle's speed.
Test conditions:
Engine idling.
Parking brake applied.
Transmission in neutral.
Coolant temperature above 30°C.
Procedure:
Start the function.
Press and hold down the gas pedal.
Let up the gas pedal when the result is shown.
Turn off the ignition.
Wait 6 seconds.
Turn on the ignition.
The function is done.
If the function fails, check the test conditions and repair any faults.