The US National Highway Traffic Safety Administration (NHTSA) is probing the 8GB memory units in some Tesla models after 12,500 car owners complained that worn-out memory was behind touchscreen failures that broke things like the rearview camera.
The probe was launched this week following a preliminary investigation opened in June by the NHTSA's Office of Defects Investigations (ODI).
The ODI's investigation focused on Tesla Model S vehicles made between 2012 to 2015 that are equipped with an Nvidia Tegra 3 processor – the Tegra Visual Control Module in Teslas – which have an embedded 8GB eMMC NAND flash memory device.
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The device powers the Tesla's touchscreen or media control unit (MCU), which in turn powers other features like the rearview camera. Once the storage is worn out, it can break other features like the touchscreen.
As noted in the NHTSA's notice to investigate, eMMC NAND flash devices wear out after a certain number of program/erase cycles.
"The subject MCU allegedly fails prematurely due to memory wear-out of the eMMC NAND flash," it said.
The affected flash devices, which power the Tesla touchscreen, are installed in about 160,000 Tesla vehicles, including 2012-2018 Tesla Model S and 2016-2018 Model X vehicles.
"The data show failure rates over 30% in certain build months and accelerating failure trends after three to four years in service," NHTSA said.
Following a request by the ODI, Tesla provided information about 7,777 warranty claims, and 4,746 non-warranty claims related to MCU replacements.
All the affected storage devices were 8GB eMMC units from SK Hynix, which are embedded in Nvidia's Tegra Visual Control Module. However, from July 27, 2020, "Tesla made the Tegra Visual Control Module (VCM) available for replacement with a 64GB Micron eMMC, avoiding a full MCU replacement ".
According to Tesla's report, the Hynix units in the Nvidia VCM "are rated for 3,000 program/erase cycles for each block of NAND flash within the eMMC".
Storage usage is affected by daily drive time, daily charge time, and use of music streaming.
"At the nominal daily P/E cycle use rate of 0.7 per block, it would take between 11 and 12 years to accumulate an average of 3,000 P/E cycles per block in the device," Tesla said.
"At the 95th percentile daily P/E cycle use rate of 1.5 per block it would take five to six years to accumulate an average of 3,000 P/E cycles per block in the device."
Which raises a question about how long these eMMC devices should last or be covered by warranty in a vehicle. And the effects go well beyond the touchscreen, according to the NHTSA.
"Tesla provided the effects of MCU failure on vehicle function, which result in loss of rearview/backup camera, loss of HVAC (defogging) setting controls (if the HVAC status was OFF status prior to failure)," the NHTSA said.
"There is also an impact on the advanced driver assistance support (ADAS), Autopilot system, and turn signal functionality due to the possible loss of audible chimes, driver sensing, and alerts associated with these vehicle functions."
Just ahead of NHTSA's investigation notice, Tesla announced a 'warranty adjustment program' for the 8GB eMMC in the MCU.
"For customer peace of mind, we are providing additional coverage on some Model S and Model X vehicles built before March 2018 that are equipped with an 8GB embedded MultiMediaCard in the media control unit," Tesla states.
"We are aware that this component may malfunction due to accumulated wear. If this occurs, it could result in a blank or intermittently blank center display, or an alert indicating that a memory storage device has degraded and to contact Service."
Tesla will repair or replace the 8GB eMMC free of charge if the issue occurs within eight years of its delivery to a buyer. But the vehicle also needs to have travelled less than 100,000 odometer miles.
Tesla notes that there is "no risk to vehicle drivability if the eMMC malfunctions, including no effect on acceleration, braking or steering, but you may lose access to features that are available through the vehicle's center display".