Having issues with “Service Trailer Brake System “ , this should be a safety concern for GM , and not up to the customer to pay for this repair.
2021 Chevrolet Silverado HD electrical problems
moderate 15 complaints filed with NHTSA · avg repair $850 · see electrical across all vehicles →
Complaints
15
Recalls
0
Avg fix
$850
When does it fail?
Of the 15 electrical complaints filed for the 2021 Chevrolet Silverado HD, here's the actual mileage breakdown — failures cluster heaviest at 50,000-75,000 mi.
0-25k
25-50k
50-75k
75-100k
100-125k
125-150k
150k+
Each bar shows the share of total complaints filed at that mileage range. Peak failure window highlighted. Some owners report problems earlier; some make it well past 150,000 miles symptom-free. Maintenance habits and driving conditions shift the curve as much as mileage alone.
What stands out
Electrical accounts for 18% of all owner complaints filed against this vehicle, across 3 categories tracked.
The failure pattern owners describe
The 2021 Silverado HD electrical system is generating complaints across multiple subsystems. The most common and hazardous is the power tailgate opening and closing unpredictably during normal operation—while driving, parked, locked, or unlocked. Multiple owners report it opens several times daily with no warning, creating a genuine safety risk if cargo is loaded. One owner's tailgate fell and dented their garage overnight within days of purchase. Owners say dealers acknowledge the problem but claim no recall applies to their VINs, or warranty has expired, leaving repair costs to owners ($170 just for diagnosis in one case).
DEF heater and electrical harness failures cause engine derating and speed limitation. Owners report melted wiring harnesses and overheating connectors; one case shows P10D9 and P20C1 codes. Recall #N212342980 exists for some vehicles but doesn't cover all affected trucks. Technicians report seeing many trucks outside the recall with identical failures.
Additional electrical issues include the transmission park-position sensor failing to register park mode (continuous false dinging), rear camera failures generating error messages weeks after purchase, no-start conditions with sputtering on a 6.6L gas engine, and persistent false trailer brake system warnings. These are described as "known issues" across 2020/2021 models with no widespread fixes offered.
Same Chevrolet Silverado HD electrical reports on nearby years: 2019 · 2020 · 2022 · 2023 · 2024
Failure modes owners describe
Tailgate opens/closes randomly
Power tailgate opens and closes on its own multiple times per day, regardless of truck state (park/drive, locked/unlocked). No user input required. Occurs while driving, at rest, and during normal operation.
When: Occurs throughout ownership; some owners report issues within days or weeks of purchase
Symptoms owners cite: tailgate opens without input while driving; tailgate closes then reopens repeatedly; tailgate partially raises then slams down; no warning before opening; notification appears after event occurs
Repairs/costs cited: One owner mentioned dealer quoted $170 for diagnosis only; some owners report warranty does not cover the issue; one owner successfully had it inspected at dealer
Recalls/TSBs owners mention: Some owners report recall #N232426400 exists but was not properly notified to all affected vehicles; dealers report 'no recall' for some VINs or state warranty has expired; owners instructed to file NHTSA complaints rather than dealership help
DEF heater/electrical harness failure
Reductant heater connector or DEF tank electrical harness overheats or melts, causing engine derating and speed limitation. Related to reductant heater circuit malfunction.
When: Reported at approximately 68,000 miles in one case; intermittent and ongoing in others
Symptoms owners cite: vehicle speed limited to 50 MPH maximum; sudden deceleration from 75 MPH to 5 MPH; heater connector causing overheat condition; wiring harness melted or damaged
Codes mentioned: P20C1, P10D9
Repairs/costs cited: Technicians report melted wiring harness is common; one technician stated seeing many trucks outside recall with same issue; repairs not covered under warranty per owner report
Recalls/TSBs owners mention: Recall #N212342980 exists but does not cover all affected vehicles; manufacturer referred owners to NHTSA Hotline instead of addressing under warranty or expanded recall
Park position not detected / continuous dinging
Park mode sensor or shift position sensor fails to register that vehicle is in park. Transmission display shows 'shift to park' and door chime continues dinging repeatedly even though vehicle is actually in park and stationary.
When: No mileage specified
Symptoms owners cite: display shows 'shift to park' when already in park; continuous dinging/chiming sound persists after closing door; chime does not stop for extended period
No-start / hard start with sputtering
6.6L gas engine cranks but will not start on first attempt, sputtering out repeatedly. Intermittent problem that resolves after approximately 30 minutes. Auto start/stop function does not engage during this condition.
When: Intermittent; first occurrence after purchase
Symptoms owners cite: engine cranks but does not start; sputtering on each start attempt; auto start/stop feature fails to activate; runs normally once started
Codes mentioned: ECM suspected by owner/forum reports
Repairs/costs cited: No repair documented; owner suspects Engine Control Module based on forum knowledge
Rear camera failure
Rear view camera stops functioning and displays error message on infotainment screen. Issue reported as widespread among 2020/2021 Silverado owners with no manufacturer fix identified.
When: Two weeks after purchase in reported case
Symptoms owners cite: camera image not displayed; error message appears instead of camera feed
Recalls/TSBs owners mention: No specific resolution or identified root cause per owner report
Service Trailer Brake System warning
Trailer brake system fault warning appears on infotainment display and chimes repeatedly. Warning persists even though vehicle may not be towing or warning may be spurious.
When: No mileage or timing specified
Symptoms owners cite: 'Service Trailer Brake System' warning displays; warning beeps/chimes continuously; warning does not clear
Recalls/TSBs owners mention: Multiple owners report this is 'known issue' but no recall or warranty coverage mentioned
Synthesized from 15 NHTSA owner complaints — unverified consumer allegations, summarized for patterns. The verbatim filings appear below.
What owners are reporting 4 most recent
The contact owns a 2021 Chevrolet Silverado 2500. The contact stated that the connector for the heater system was causing the vehicle to overheat, subsequently enabling the vehicle to go faster than 50 MPH. If the vehicle reaches 75 miles, it would immediately decrease in speed to 5 MPH. The vehicle was taken to a certified mechanic who diagnosed a P20C1 code, indicating reductant heater failure…
It's a known issue that 2020 and 2021 Chevy Silverados have a malfunction in the tailgate where it automatically opens while driving, opening the driver-side door, or even locking and unlocking the vehicle.
We believe that it is the park sensor in the column . When you place the truck into park, the screen displays the words shift to park period and the dinger.Inside the truck continues to ding for a long time, even with opening and closing the door ... The truck is actually in park, so it does not move.But the display says it's not.And apparently it is not registering because it keeps dinging
Had electrical trouble with your 2021 Chevrolet Silverado HD?
File a complaint with NHTSA → It's free, official, and how every report above got here — owner filings are the federal safety record this page is built on.
Common questions
How serious is the electrical problem on the 2021 Chevrolet Silverado HD?
It's a documented issue but not catastrophic. 15 complaints have been filed. Repairs average $850 and most owners catch it before it causes a breakdown.
At what mileage does the electrical typically fail?
Based on the 15 complaints filed, electrical issues most often appear around 34,828 miles. Some report problems earlier; some make it well past 150,000 with no symptoms. Maintenance habits matter — vehicles that received timely fluid services and were not regularly overworked tend to last longer.
What does it cost to fix?
Independent shops typically charge around $850 for electrical repairs on this vehicle. Dealer pricing tends to run 20-40% higher. The exact figure depends on the specific failure mode, parts availability, and your local labor rates. If you're outside factory warranty, an extended service contract often covers this category.
Are there any recalls related to electrical?
No active recalls currently cover electrical issues on this vehicle. The complaints filed represent owner-reported failures that haven't risen to the level of a manufacturer-issued recall — but they're still worth knowing about before you buy or budget for repairs.
Related
Complaint and recall data sourced from the National Highway Traffic Safety Administration (NHTSA)
public records database. Verify the raw federal record at
nhtsa.gov/vehicle/2021/Chevrolet/Silverado HD.
Severity ratings are derived from reported crashes, fires, injuries, and fatalities. Repair cost estimates are
independent-shop national averages and may differ in your area. Some links on this page are affiliate links.