DJI motor or propeller error: check propellers warning

A DJI motor or propeller error usually means a propeller is on the wrong motor, a blade is damaged, or something is stopping a motor from spinning freely. DJI says a drone with incorrectly mounted propellers can't take off. Power off, check that each propeller matches its motor, replace any damaged blade, and spin each motor by hand to feel for grit. If a motor is still rough or won't start, the drone needs a repair.

Propeller problem or motor problem? — Most motor and propeller warnings come from props fitted to the wrong motor, damaged blades or grit in a motor. A motor that won't turn smoothly by hand needs DJI service.

Propeller installation errors

DJI's propellers come in two types that spin in opposite directions, and each type belongs on specific motors:

Mini 3, Mini 4 Pro: propellers with a raised mark go on the motors with a mark. They're held by screws, using the included screwdriver.
Mavic 3 series: propellers with white rings and propellers without them go on different motors and twist on in opposite directions. DJI's guide shows which is which relative to the camera.
Air series: propellers come as type A and type B. DJI says to unfold the front arms first, then the rear arms, and not to install the props reversed.
Mavic 4 Pro, Flip: propellers come pre-installed. Replace damaged ones following DJI's video tutorial.
Mini 5 Pro, Neo: follow DJI's video tutorial for your model when fitting new props.

A prop on the wrong motor pushes air the wrong way, so the drone can't lift off or flips as it tries. Fitting help is in how to change DJI propellers.

Motor errors and "starting motor failed"

DJI's help center gives three causes for a motor that won't start: propellers installed wrongly, debris inside the motor, or a faulty motor. Its fixes:

Check the propellers and try fresh ones.
Look for sand or dust inside the motor and clean it out.
With the drone off, rotate each motor by hand. If it doesn't turn smoothly, send the drone in.

Use a hand blower, not compressed air at close range, and don't poke tools into the motor.

Other things to check

Restricted zones. DJI lists GEO restricted zones as a reason motors won't start. Check the map in DJI Fly. See drone won't take off.
Loose or worn props. DJI says to replace propellers that are damaged, misshapen, corroded or loose.
Propeller guards. A bent guard that touches a blade can stall a motor. Refit it or remove it.
Uneven shutdown. DJI treats a gap of more than 2 seconds between a motor stopping and its propeller stopping as a fault to check.

When it needs repair

Start a repair if a motor grinds, has play in the bell, runs much hotter than the others, or the error survives new props and cleaning. If the warning reads as an ESC fault, read DJI ESC error. Spare props are cheap insurance: Air 3 and Air 3S pilots can keep a pair of Air 3 Series Low-Noise Propellers in the bag, and consider the Mini 4 Pro 360° Propeller Guard for flying close to trees.