General Motors recently issued a new Service Update for a select number of electric vehicles, including the GMC Hummer EV and GMC Sierra EV. This new bulletin outlines potential problems with trucks’ high-voltage battery systems. While not classified as a recall, this update highlights a manufacturing issue that may affect the way certain electrical connections are sealed within the battery pack.
According to a new Service Update (marked as bulletin N252529080), a small number of Hummer EV and Sierra EV units may be built without a critical connector within the high-voltage connector, located in the rechargeable energy storage system (RESS). Affected units were manufactured between the 2024 and 2026 model years for both nameplates. GM notes that only a small percentage of vehicles included in the bulletin are expected to be impacted by this issue.
As noted above, this is not a safety recall, but rather GM is instructing dealers to address this issue during routine service visits, or, as the case may be, while the vehicle is still in stock.
To resolve this issue, the technician will first check the relevant high voltage connector and ensure that the header connector is present and installed correctly. If components are missing or incorrectly installed, they will be replaced using approved service parts. Only technicians with special high voltage training are authorized to perform repairs. The bulletin estimates that the repair procedure will take approximately 1.7 to 1.8 hours to complete, with most of that time spent dismantling the high-voltage system.
GM estimates less than two percent of affected vehicles will require replacement parts. Several GM EVs are included in the bulletin, including the Chevy Silverado EV and BrightDrop EV, as well as the Escalade IQ, as previously discussed.
As a reminder, the Hummer EV and Sierra EV are both powered by the GM BT1 platform, with production taking place at GM’s Factory Zero plant in Michigan.
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