Service High Voltage Warning Message

[super8]

Well, 2 months and 2 payments in, I got the dreaded "Service High Voltage " warning message pop up. It seems to drive find, but won't charge. So looks like another trip to the dealer next week.

 

[super8]

This was meant to be GM’s solution, but unfortunately, it didn’t work in my case

Check if you see a red icon in your instrument cluster that looks like a vehicle with an exclamation mark on it and/or one of these messages:
1. “Service Vehicle Soon”
2. “Unable to Charge”
3. “Service High Voltage System”

These messages can mean there is a problem with your battery cooling system and that your vehicle needs service.
However, they can also occur when the battery cooling system encounters an error. If the red light appeared while you were driving, you can troubleshoot it yourself.

IMPORTANT: Before trying to troubleshoot, make sure your vehicle is parked in a safe location. Depending on the error, you may not be able to restart your vehicle after turning it off.

Here’s how to check if there’s a problem with the system or if it’s an error you can fix:
1. Turn your vehicle off.
2. Open and shut the driver door.
3. Wait 30 seconds. During this 30 seconds, your vehicle’s software will attempt to fix the problem.
4. After 30 seconds, turn the vehicle back on. You may still see the red warning light in your instrument cluster, but your heat/air conditioning should turn back on and your vehicle should start charging again.
5. Turn the vehicle off and back on again. The red warning light should disappear. If it does, your vehicle is safe to charge and drive.
You might see the red warning light and your heat/air conditioning might not work after turning your vehicle on after not driving it for a few hours. In that case, try the following steps to determine if there’s an issue:
1. Turn the vehicle on and off five times, waiting 30 seconds between turning it off and turning it back on again.
2. After five on/off cycles, the light should go away and your heat/air conditioning should turn back on.
3. If not, contact your Dealer to schedule service.

 

[Dragoon]

That's a buzzkill! Hopefully, it's a quick fix for the dealer, and they don't have to have it for long.

 

[Helipilot]

They left out…Do the Hokey Pokey and turn yourself around

 

[Georgiy]

Every time after washing the truck, it does not charge the truck. Returns an error . Then after some time, 5-6 hours, the error disappears. Who have you had this situation with? Please tell me who solved the problem.

 

[Georgiy]

I have the same mistake, every time after washing the truck, I began to put the bag in the charging slot, before washing, so that no water would get in.

 

[Georgiy]

I really look forward to your information from the dealer on this issue.

 

[super8]

Great news, the Hummer seems to have fixed itself! After a 15-minute drive and a quick 10-minute park, the error message disappeared when I restarted. Everything’s working fine now, and it even charged without any issues last night.

 

[Georgiy]

Great news, the Hummer seems to have fixed itself! After a 15-minute drive and a quick 10-minute park, the error message disappeared when I restarted. Everything’s working fine now, and it even charged without any issues last night.

And how did you reboot it?

 

[super8]

And how did you reboot it?

I didn't have to, but if you disconnect the battery in the frunk, that should reboot/reset everything.

 

[Plev22]

Curious if your issue is resolved. Mine was giving same message as well as charge port failure. I disconnected negative on 12v battery and it cleared and now charges and heat works again. It charged fine overnight, but this morning was giving the error I even unplugged it. I did link the car to the ev.energy app yesterday to get rebates from electric company. Wondering if that had something to do with error. I have since unlinked it.

 

[Eman32708]

View attachment 595

Well, 2 months and 2 payments in, I got the dreaded "Service High Voltage " warning message pop up. It seems to drive find, but won't charge. So looks like another trip to the dealer next week.

That happened to me after I took it to the dealership to have package lights installed. They wouldn't admit they caused the problem but ended up keeping the truck for 3 weeks and replaced the battery. It only had 2,000 miles at the time.

 

[Cheesehead]

That happened to me after I took it to the dealership to have package lights installed. They wouldn't admit they caused the problem but ended up keeping the truck for 3 weeks and replaced the battery. It only had 2,000 miles at the time.

My 2025 SUV has same high voltage system warning, at dealer for 1 wk and counting.

 

[Dragoon]

My 2025 SUV has same high voltage system warning, at dealer for 1 wk and counting.

Sorry to hear this! Did they give you a date when they think it would be fixed?

 

[Cheesehead]

Sorry to hear this! Did they give you a date when they think it would be fixed?

They rec’d HVbattery on Feb 13 (Fri) and said the tech person hopes to complete it on Feb 16 (Mon). I’m reading about dealerships that take weeks to install due to lack of experience installing HVbatt’s vs. 1 day to install if that dealership has done installs before.
I’m concerned about why it failed when it was engineered for 8-10 year lifecycle: water intrusion, wiring issue, part failure, etc.
I’m sending cert mail to GMC for Motor Vehicle Defect Notification.
Dealership is horrible and then some. I did talk directly to the Service Mgr.
Started Jan 26th, starting week 4 on Monday (16th).

 

[Cheesehead]

Got Hummer back after 22 days, the paperwork says faulty sensor. They replaced the HV battery. If that’s true, they better move that sensor so they can service it without replacing the entire battery.