Owners of several different BrightDrop, Chevy, and GMC EVs produced by GM may hear a grunting or clunking noise when utilizing the Adaptive Cruise Control (RPO code KSG) or One-Pedal Drive systems in “stop-and-go traffic,” according to a recent NHTSA bulletin.
However, these GM EV grunting noises are normal during operation of vehicles equipped with noted technology, Service Bulletin 24-NA-034 says, and owners should not take their EV to the dealership, since the service department will decline to provide service.
According to the bulletin, the grunting or clunking sounds are produced when driving at 5 miles per hour while using Adaptive Cruise Control or One-Pedal Drive, when making a very brief stop that involves decelerating to a halt or near-halt and then accelerating again immediately, or when tapping the accelerated pedal while the vehicle is stopped.
These sounds are completely normal for these situations and are simply the anti-lock braking system (ABS) working to stop the vehicle. The sound may be louder if the vehicle in front of the EV where the noise is occurring is close to the EV’s front end, and quieter if the next vehicle is farther away.
The NHTSA says that the following models can be affected by this unexpected ABS grunting noise:
- 2023 BrightDrop Zevo 600
- 2024 BrightDrop Zevo 400
- 2024 BrightDrop Zevo 600
- 2025 Chevy BrightDrop 400
- 2025 Chevy BrightDrop 600
- 2024 Chevy Blazer EV
- 2025 Chevy Blazer EV
- 2023 Chevy Bolt EV
- 2023 Chevy Bolt EUV
- 2024 Chevy Equinox EV
- 2025 Chevy Equinox EV
- 2024 Chevy Silverado EV
- 2025 Chevy Silverado EV
- 2022 GMC Hummer EV Pickup
- 2023 GMC Hummer EV Pickup
- 2024 GMC Hummer EV Pickup
- 2025 GMC Hummer EV Pickup
- 2024 GMC Hummer EV SUV
- 2025Â GMC Hummer EV SUV
- 2024 GMC Sierra EV
- 2025 GMC Sierra EV
The bulletin and list of vehicles was originally released in February, but has been updated and expanded in November 2024.
The sound occurs regardless of whether the vehicle has 2WD, 4WD or AWD. The owner can potentially reduce the sound by adjusting the cluster menu gap settings to “far,” but the grunting or clunking noise will continue to be present at some level.
Comments
LOL.
I’ve now put more than 25,000 miles on two different Bolt’s. Both 2023’s. The first didn’t have the adaptive cruise like my second one, but they both use OPD. I use the OPD all the time and the ACC now and then. I’ve never heard any such noise.
Oh, we meant to do that.
“It’s normal” and “Turn the radio up” are time-proven outs in this industry.
And not just GM: ask Ford about that Focus transmission…
(Jeremy Clarkson as narrator):
That sound, when you think about it… Well, it let’s you know that something special is going on with your otherwise silent ride. Like a ‘mark of excellence’ that might get you to appreciate your car just a little more.