Hummer EV Power Loss Linked to High-Voltage System

As someone with moderate experience maintaining EVs, I encountered a similar issue with a 2021 GMC Hummer EV Pickup. The symptoms matched yours, power reduction followed by system shutdown and high-voltage warnings. The root cause in my case was a voltage sensor malfunction combined with a battery drain issue. Initially thought it was cable damage in the electrical wiring, but diagnostic testing revealed the actual problem. The inverter issue triggered false readings, making the system think the battery was heavily discharged. The repair involved: Full system diagnostic, Voltage sensor replacement, Battery system recalibration, Software update Total cost came to 290 Euro and took about 2 days to fix. The workshop found that the voltage sensor was sending incorrect signals to the power management system, causing unnecessary shutdowns. To better assist with your specific case, could you provide: Complete error codes from the system, How long the vehicle runs before showing warnings, Whether the issues occur more frequently in certain weather conditions, If you notice any unusual sounds from the high-voltage system This information would help determine if your issue matches what I experienced or points to a different electrical system problem.

Current mileage 65075 KM, last service performed in November 2023. Thanks for the detailed reply. After reading about your experience, I checked for similar symptoms. In my case, the EV problem starts within 10 minutes of driving, with the battery warning appearing suddenly. No unusual sounds precede the shutdown. The main error code is E-4582 (high voltage system). The electrical fault seems worse in cold weather, which makes me think your voltage sensor theory could be right. When the car shuts down, I get error messages about restricted power output and system protection mode. A basic scan revealed potential cable damage near the main power distribution unit. Getting it checked at the service center next week, will update once I know more about the battery drain situation. Has anyone else had the system protection mode trigger specifically in cold weather?

Thanks for the additional details. The cold weather correlation with your electrical fault matches what I experienced exactly. My GMC Hummer EV also showed the E-4582 error code and system protection mode in similar conditions. From your description, the symptoms strongly suggest a voltage sensor issue rather than cable damage. In my repair case, the mechanics initially suspected wiring problems too, but the battery warning and sudden power loss were actually triggered by faulty sensor readings amplified by cold temperatures. A few key points about my repair experience: The system protection mode activated most frequently below 5 degrees, Initial voltage readings were unstable, Battery drain appeared worse than actual levels, Sensor replacement resolved both the shutdown and power restriction issues The timing of your problems (10 minutes into driving) is remarkably similar. Before the repair, my inverter issue would also trigger early in the drive cycle as the high-voltage system reached operating temperature. Quick tip, if possible, record when the electrical fault occurs in relation to battery temperature. This data helped my service center pinpoint the root cause faster. Looking forward to hearing what your service center finds. The 65000km mark is when several owners reported similar sensor-related electrical faults in these units.

The error code E-4582 with battery warnings matches what others described. These symptoms appearing 10 minutes into driving, especially during cold weather, definitely points to voltage sensor problems rather than actual cable damage. Based on the extensive feedback, I feel more confident about the service center visit next week. The high-voltage system warning behavior and restricted power output sound identical to cases where faulty sensors triggered the system protection mode. Will get them to focus on testing the voltage sensors and checking for any inverter issues during cold starts. This input has been really helpful for narrowing down the likely causes of the EV problem. Makes sense that these electrical faults show up around the 65000km mark. Planning to document the exact conditions when the battery warning appears and record the system behavior during cold starts. Will post an update after the service center diagnoses the exact fault in the electrical wiring system. Thanks for sharing the repair details and costs. Anyone else experiencing similar shut downs should definitely get their voltage sensors checked, especially if the issues worsen in cold conditions.