After 12,523 replacements, Feds investigate Tesla Media Control Unit failures

November 17, 2020 by No Comments

Getty Images/Jonathan Gitlin

Is one of Tesla’s infotainment systems defective by design? That’s a question the National Highway Traffic Safety Administration hopes to answer. It has started an engineering analysis after hundreds of customer complaints of bricked systems resulted in a preliminary investigation in June.

NHTSA thinks it knows what the problem is: an 8GB eMMC NAND flash memory chip—an SD card in other words—with a finite number of write cycles, fitted to its Media Control Unit. The MCU regularly writes logs to this chip and, within three or four years, reaches the lifetime number of cycles. At this point the touchscreen dies, taking with it functions like the car’s backup camera, the ability to defog the windows, and also the audible alerts and chimes for the driver aids and turn signals.

After the regulator’s Office of Defects Investigation received 537 complaints, it asked Tesla if it knew of any more problems with the Nvidia Tegra 3-based system, which is fitted to approximately 158,000 Models S (2012-2018) and X (2016-2018). Tesla did, handing over 2,399 complaints and field reports, 7,777 warranty claims, and 4,746 non-warranty claims.

The finite—and short—lifespan of these infotainment systems is a relatively well-known problem within the Tesla community. A video on the popular YouTube channel Rich Rebuilds that delved into the problem in May 2019 has racked up more than 669,000 views:

The discussion of the infotainment system failures begins around 9 minutes in.

As that video notes, and as Tesla told NHTSA, the time to failure for an MCU depends on how much its car has been in operation. Daily drive time, daily charge time, and streaming music over the Internet are all factors, Tesla told the regulator.

This isn’t the first time that Tesla’s choice of consumer-grade electronics, as opposed to automotive-grade, has gotten it in trouble. A separate problem affects the 17-inch touchscreen, which can fail due to high temperature—the kind of temperature experienced inside a parked car during summer, as opposed to an air-conditioned office.

But how the infotainment system’s code was written is a factor here, too. In 2018, a poster at the Something Awful forums who claimed to be a former Tesla software developer whose NDA had now expired, detailed a litany of similar problems with the company’s approach to software, including other problems caused by excessive logging.

Tesla has attempted to remedy the problem with at least six OTA updates between July 2019 and October 2020. These have reduced the amount of logs being written, improved error correction and storage strategies, changed the control logic for the turn signals, and even added a default to set the climate control to 71.6˚F (22˚C) in the event of an MCU failure (to prevent windshield fogging). In May of this year, Tesla began producing spares that now use a 64GB Micron eMMC SD card instead of 8GB SD cards from Hynix.

The automaker told NHTSA that as of firmware 2020.20, each block of NAND flash should only receive 0.7 read/write cycles a day, which would therefore take between 11 and 12 years before the chip reached its end of life. However, owners who use their cars more often could see this time before failure halved.

However, Tesla also told NHTSA that “the MCU failures are likely to continue to occur in subject vehicles as vehicles continue to operate and use available memory in the 8GB eMMC NAND flash memory until 100 percent of units have failed.” Given the safety-critical nature of the problem—specifically the loss of defogging—an official recall may well occur in the coming months.

Ars could not reach Tesla for comment as the automaker eliminated its entire press office in October.

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