What does drivetrain malfuntion means in a BMW?

You're driving along at a leisurely pace when suddenly a message appears in full screen on your BMW's iDrive: "Drive moderately. The powertrain cannot deliver full power!"

You get the idea to turn off and restart the car, and the message disappears! But what exactly happened?

The "powertrain" message is a warning that accompanies what is commonly referred to as "limp mode" or half-engine light. This is a protection mode for the car's engine that results in reduced performance, turbo deactivation, and much more.

The mode is triggered when engine operating conditions become unacceptable to prevent engine damage. But why doesn't the message reappear after restarting?

That's because the protection function operates in real time only. When the message appeared in your car, the engine was at a certain number of revolutions per minute (RPM), at a certain power level, and there was a noticeable deviation between the current condition of one of the multiple monitored parameters and the maximum allowable values.

It is important, after such a message appears, to have the car checked by a specialist. Even if the "check engine" light has not come on, the car may be at the beginning of a major problem. You should also know that the "check engine" light only comes on to indicate that there is a problem that is causing the car to exceed emission standards. A mechanical or electrical problem does not necessarily affect emissions, but letting it go uncheck can still be quite expensive.