GM TSB: “Service High Voltage” Warning on Silverado EV & Sierra EV (What It Means + Fix)
If you own a Chevy Silverado EV or GMC Sierra EV and suddenly see a “Service High Voltage” message along with a check engine light (MIL), you're not alone.
GM has released an official Technical Service Bulletin (TSB) addressing this issue and the good news is, it’s typically not a hardware failure.
This article breaks down what’s happening, what codes are involved, and how dealers are fixing it.
The Official TSB
This information is based on GM bulletin:
TSB #26-NA-031 (March 6, 2026)
The bulletin applies to multiple GM EVs, including:
- Chevy Silverado EV (2024–2025)
- GMC Sierra EV (2024–2025)
- Blazer EV, Equinox EV, Hummer EV, Cadillac LYRIQ, and others
Symptoms You Might See
According to the bulletin, owners may experience:
- “Service High Voltage” message on the dash
- Check engine light (MIL) illuminated
- No obvious drivability issues in many cases
Technicians often find communication-related trouble codes such as:
- U2220 – U2237 range
- U2C11
These are network communication faults, not necessarily component failures.
What’s Causing This?
GM’s official diagnosis:
A software anomaly in the battery energy control system.
In plain English: your truck’s high-voltage system modules aren’t communicating correctly due to software and not because something physically broke.
The Fix (What the Dealer Will Do)
The repair process outlined in the TSB includes:
1. Software Update
The dealer will reprogram the K16 Battery Energy Control Module (BECM) with the latest software calibration.
2. Manual Reset Procedure
This is the important part and likely why some vehicles needed repeat visits before this TSB existed.
The reset includes:
- Disconnecting the 12V battery (following GM procedure)
- Waiting 15 minutes
- Reconnecting the battery
- Cycling the vehicle into “Ready” mode
- Repeating the process twice
This ensures all modules fully reset and sync correctly.
⚠️ Important Safety Note
Before disconnecting the 12V battery, the vehicle must NOT be in Battery Maintenance Mode. See my recent blog post on the importance of disconnecting the 12v battery safely and properly.
If it is:
- The high-voltage system may still be active
- The 12V cables can be energized
- This could result in shock or damage to components
This is why GM specifies this as a dealer-level repair in the bulletin.
How Long Does This Take?
GM’s labor estimates:
- 1.5 hours for reset procedure
- 0.4 hours for programming
Realistically, expect half a day at the dealership.
Is This Covered Under Warranty?
Yes, this repair falls under:
- Bumper-to-bumper warranty coverage (if applicable)
No parts are required as this is a software + reset fix.
Should You Be Concerned?
Short answer: Not really, but don’t ignore it.
This issue is:
- Software-related
- Fairly widespread across GM EVs
- Fixable with updated programming
However, since it involves the high-voltage system, you should still get it addressed promptly.
My Take (Owner Perspective)
This is a good example of something we’ll likely continue to see with newer EV platforms:
- Complex software interactions between modules
- Communication faults triggering warnings
- Fixes delivered via software updates + reset procedures (hopefully OTA)
The important takeaway is that this does NOT mean your battery is failing.
It’s much closer to a “software glitch” than a hardware issue.
Final Thoughts
If you see a Service High Voltage message in your Silverado EV or Sierra EV:
- Don’t panic
- Document any codes if possible
- Schedule a dealer visit referencing TSB #26-NA-031
This will help the service advisor get you to the correct fix faster.
Got questions? Drop a comment I love hearing from all of you.
If you found this useful:
- please considering buying me a coffee to help support future content
- Did I get something wrong? Let me know in the comments section or visit our Link Tree to contact us.
- Also, please consider visiting our EV Accessories store to support us.
