A parasitic draw on your GMC Hummer EV Pickup usually points to the 12V battery, a module that won’t sleep, or an aftermarket add-on. Here’s how to narrow it down and when to park it.
Why your Hummer EV wakes up and drains
If your GMC Hummer EV Pickup is dead or sluggish in the morning, the high-voltage Ultium pack is rarely the first suspect. The truck's computers, telematics, door modules, infotainment, and even the key fob receiver run off the 12V battery. When one of those stays awake—or the 12V battery is weak—the truck can pull a parasitic draw all night. Common culprits include a failing 12V battery, OnStar or telematics keeping the truck online, a software or OTA update that didn't finish, a door, frunk, or tailgate latch not fully closed, a key fob left inside or too close to the garage, and aftermarket dash cams, alarms, or GPS trackers wired to constant power.
Read the full breakdown in the Knowledge Base
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