A Mustang Mach-E bug leaves cars stuck in 'deep sleep' with an empty 12v battery

The bug drains the car's secondary battery even when it's plugged in and charging.

Andrew Tarantola / Engadget

Add a software bug to the list of issues affecting Ford's recently released Mustang Mach-E electric crossover. Per The Verge, a problem with the car's secondary 12-volt battery is leaving some vehicles unable to start, even when their primary lithium-ion battery is fully charged. In normal circumstances, the battery pack will pull energy from the car's primary power cell. With Mach-E vehicles where this is a problem, that doesn't happen when the car is plugged in and charging. When the 12-volt battery eventually dies, the FordPass app will report the Mach-E is in a "deep sleep" mode.

Ford acknowledged the issue in a technical service bulletin filed with the National Highway Traffic Safety Administration, where it notes the problem is a software-related issue with the car's powertrain control module. The company claims the bug only affects a "small number" of Mach-E vehicles. Specifically, those Ford manufactured on or before February 3rd. And while the automaker is developing an OTA to address the issue, the primary way to resolve the problem is to bring an affected Mach-E to a Ford dealership. It's possible to jumpstart the battery yourself, but the process for doing so is not at all straightforward.

"We are aware that a small number of Mustang Mach-E owners have had their 12-volt battery reach a low voltage condition. We proactively worked with early owners experiencing this issue to identify the root cause and a fix," a Ford spokesperson told Engadget. "In the rare instances where this still occurs, customers can now contact their local EV-certified Ford dealer to have the matter resolved."

When it comes to recently released EVs, software issues are not uncommon, especially among automakers relatively new to making them. Late last year, Polestar had to recall the Polestar 2 to address a software glitch that caused some vehicles to lose power suddenly while driving. Still, no matter how small this latest bug is, it's a blip for one of the high-profile EV launches from a US automaker.