A bidirectional driver can control both motor terminals. Measuring one terminal against chassis ground does not by itself describe the voltage acting across the motor.
How to narrow it down
Use the correct circuit and suitable measurement arrangement to compare both output terminals with the command and current. A specialist can then distinguish a missing drive condition from a misleading reference point. This matters on powered locks, seats and other reversible actuators.
What to include with the fault report
Send the affected function, circuit information and the exact measurement points.
Do not connect common-ground test equipment across switching outputs without checking its suitability. An incorrect connection can short the driver.
Speak to AXION
For complex vehicle-electronics diagnostics, send your vehicle details and fault report. Workshop assessment is in Didcot, Oxfordshire. Suitable postal or remote work is confirmed before booking.
Technical background from Texas Instruments. The referenced design explains the principle; the vehicle-specific procedure determines the repair.
Related reading — Motor braking and coasting can produce different stop waveforms. Browse all vehicle-electronics diagnostic notes or return to the repair library.