After GMC announced in August that there was a problem with the Hummer EV’s high-voltage connector that could allow water into the battery pack, the automaker is facing another similar problem. Apparently, water could still get inside Hummer EV battery packs due to improper sealing, which could cause the vehicles to either not start or suddenly lose power during operation.

The recall affects 735 GMC Hummer EVs, but also 89 BrightDrop EV600 electric vans, as both vehicles are built on General Motors’ Ultium platform and have similar battery packs (manufactured by Magna). The automaker says it is aware of three instances when this manufacturing defect caused problems.

2022 GMC Hummer EV's Ultium battery pack

GMC Hummer EV battery pack.

GM notes that the root cause of the issue has to do with improperly primed or electrocoated battery pack flanges “inhibiting proper adhesion of the urethane sealant.” The recall report published by the National Highway Traffic Safety Administration (NHTSA) adds that “vehicles equipped with high voltage battery pack enclosures produced outside of the supplier’s suspect manufacturing window are not included in this recall.”

The affected electric Hummers were produced between November 9th, 2021 and September 28th of this year, while the affected EV600 vans were manufacture from March 3rd through June 24th of 2022.

If water has entered affected vehicles’ battery pack and caused a malfunction, the Hummer will display warning lights and messages its the main display to alert the driver. GM says that it doesn’t have any knowledge of this defect having caused a battery pack fire and no injuries are reported.

However, given the fact that it can cause a sudden loss of power, it definitely poses a safety risk. The company has yet to announce what its fix for the problem could be - either repairing faulty battery packs or replacing them altogether - and it estimates that it will begin notifying owners of affected vehicles starting on October 28th.

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