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Just a few months after the first official deliveries of the long-awaited Tesla Semi to PepsiCo and Frito-Lay in December, the truck has been hit with its first recall. The electronic parking brake valve module (PVM) may not move into position when the truck is put into park, meaning that otherwise parked trucks can roll away.
According to the NHTSA, just 35 trucks are affected by the recall. There aren’t too many solid technical details about the Tesla Semi, so the recall is a rare look into a subsystem of the elusive truck. It certainly uses air brakes like most traditional commercial trucks, but it also blends in regenerative braking from its tri-motor system that uses a twin-motor axle that is geared for acceleration and another single-motor axle geared for highway cruising.
The recall text calls the system an electronic parking brake, but commercial vehicles with airbrakes don’t generally use a traditional electronic parking brake like you would see on a car. With air brakes, the system fails at full application, meaning that if the system loses air pressure, the brakes will be locked because of springs that act on the brake friction surfaces.
There are multiple air circuits on a semi-truck braking system, and there is a dedicated parking brake air circuit that holds the physical spring brakes back. It’s unclear if the Tesla Semi uses this exact system, but the Department of Transportation (DOT) mandates a yellow-colored parking brake valve that functions in the way described above, and the Tesla Semi has one at the driver’s right hand based on photos of the interior. Whether there is a supplemental electronic brake is also unclear, though the fact that it is a parking brake valve rather than an actuator or motor is a strong clue for it being based around the air brakes.
Tesla will replace the PVM in affected trucks free of charge and notify affected operators by May 23.
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