The National Highway Traffic Safety Administration (NHTSA) has reopened an investigation into alleged unintended acceleration on Tesla vehicles following a petition received by the Office of Defects Investigation (ODI) on June 29, 2023.

The investigation covers around 1.8 million vehicles in the US, covering nearly every Tesla Model S, Model X, Model 3, and Model Y sold in the country.

Interestingly, this reverses an earlier decision by the NHTSA to deny a call for further investigation into unintended acceleration in Tesla EVs after complaints from customers. In January 2020, the NHTSA received the original petition calling for an investigation into Tesla unintended acceleration, but safety regulator denied it a year later.

The new petition that made the NHTSA change its mind was sent by Roland Belt of Plymouth, Minnesota, and it allegedly includes new information about the inverter design. According to Belt, whose petition was first reported on by Autoevolution, recent open-source research has allowed a greater understanding of the component's function.

 

Based on this, the petition claims that a design flaw in the inverter allows for intermittent higher electrical current to flow through a vehicle's 12-volt electrical system. This sudden additional voltage draw could be triggered by demand for extra power from an accessory, preventing Tesla's diagnostics system to identify it as a fault, Belt noted in the petition.

This fault would explain some or all the unintended acceleration incidents reported by Tesla owners in the US, the petition claims.

Pending the results of the investigation, it's worth noting that Belt's claims have been dismissed by some Tesla hackers, who claim that the inverter design cited in the petition is not similar to what Tesla uses.

 

Jason Hughes (@wk057), who is known for his work on Tesla battery packs and other hardware said on Twitter that he doesn't believe that a drop in the 12-volt rail voltage can cause a calibration error triggering an unintended acceleration event.

"Tesla's accelerator pedal power, while derived from the 12-volt system, is using two independent isolated 5-volt supplies. There is no way for a fault in that system to create the correct signals for full acceleration. It's not possible. If somehow the 12-volt system were so low it caused the isolated 5-volt supplies and their capacitors to drop below the expected voltages, that'd sag the entire curve of the dual sensors, leading to a pedal fault, not full acceleration."

Green (@greentheonly), another famous Tesla hacker, believes that the claims in the petition should be easy to verify if by anyone who has a spare inverter controller PCB (printed circuit board). 

The NHTSA's investigation will probably include that test and many more to verify if the claims in the petition are true. We'll keep you updated with the results of the investigation.

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