On two separate occasions, the truck has been dead when attempting to crank. There were no lights or devices left on after the previous time the truck had been used. Something is drawing power from the battery causing it to be dead. After recharging the battery, the check engine codes read that there is a problem with 'brake light illumination.' help in determining wha t is causing the…
2020 GMC Sierra electrical problems
severe 50 complaints filed with NHTSA · avg repair $850 · see electrical across all vehicles →
Failure mileage
Complaints
50
Recalls
0
Avg fix
$850
2fires
1injury
When does it fail?
Of the 50 electrical complaints filed for the 2020 GMC Sierra, here's the actual mileage breakdown — failures cluster heaviest at 0-25,000 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
Owners have filed 50 electrical complaints with NHTSA against this vehicle, but no formal recall covers the issue — the federal record reflects what manufacturers have admitted, not everything owners are reporting.
No new NHTSA electrical complaint has been filed on this vehicle in over 5 years — the issue may be aging out of the active population.
The failure pattern owners describe
Owners of the 2020 GMC Sierra report widespread electrical issues affecting engine management, power delivery, and safety systems. The most dangerous reported failure involves wiring harness damage from factory assembly—sharp plastic ECM brackets chafing and cutting wires that should never contact them, causing complete engine shutdown at highway speeds with zero warning. Multiple owners report this exact scenario at 39,000–80,000 miles, and dealer techs confirm it's recurring across numerous GM trucks.
Battery drain is common and severe, with some vehicles dead after a week with no accessories running and no clear cause. One owner needed multiple jump starts and 3+ hours of runtime to charge enough to start, blamed on a software update that left the CPU drawing power.
Brake system electrical failures trigger "Brake System Failure" messages limiting speed to 20–62 mph, sometimes with actual loss of power assist. Owners note a 2019 recall for the same failure doesn't cover 2020 models. Check engine lights and multiple warning messages (ESC, ABS, power steering) often illuminate together with no diagnostic codes found, even after dealer hours of work.
Wiring arching and fire hazards appear repeatedly—burning smells, melted wires under the hood, and in one case a front windshield shattered from heat. Emissions system failures (code P2C7A) persist even after component replacement. Rear sliding window electrical failures cause water intrusion, corroding modules and causing mold.
Backup camera and infotainment displays malfunction—too bright at night (unusable), going blank during use, flickering, or staying on while driving. Blind spot sensors false-alarm with no vehicles present. One owner describes accelerating danger from transmission locking, door lock failures, and sensor issues after rain or car washes.
Same GMC Sierra electrical reports on nearby years: 2017 · 2018 · 2019 · 2021 · 2022
Failure modes owners describe
Engine wiring harness chafing and cutting
Factory-installed wiring harness routed over sharp plastic ECM mounting bracket, causing wires to chafe, cut, and eventually fail, leading to complete engine shutdown with no warning.
When: 39,000–80,000 miles
Symptoms owners cite: Complete engine shutdown at highway speed with no warning; No check engine light before failure; Loss of power steering; Burning smell near engine; Wires visibly damaged or melted
Repairs/costs cited: Wire harness replacement; fuel pump replacement in some cases. Costs not stated by owners. One owner paid $865.42 plus towing out-of-pocket after dealer refusal.
Recalls/TSBs owners mention: No recall issued; dealer confirms this is recurring on multiple GM trucks. No factory correction documented.
Electrical fire from wiring arching
Chafed wiring harness arches and ignites, producing smoke and burning smell from under hood. In one case, all engine wires melted completely, causing front windshield to shatter from residual heat.
When: 32,000 miles reported
Symptoms owners cite: Smoke emitting from under hood; Burning smell in cab and under hood; All wires melted; Burnt plastic under vehicle leaking residue; Front windshield shattered from heat
Repairs/costs cited: Vehicle declared factory defect at collision center; not repaired. Insurance referred claim after inspection.
Recalls/TSBs owners mention: Manufacturer notified but refused assistance citing expired warranty. No recall.
Battery drain—unable to hold charge
Battery goes dead overnight or after sitting one week with no accessories or lights on, and will not hold charge for starting. Some cases follow software updates.
When: Early ownership; one case at 6 months old
Symptoms owners cite: Battery completely dead after vehicle sits unused; No lights or accessories left on; Battery tests fine when recharged but drains again; Multiple jump starts required; 3+ hours of running needed to recharge enough to start
Codes mentioned: Brake light illumination code (reported after recharge)
Repairs/costs cited: Battery replacement in some cases, though new battery still drains. One owner suspects ECM not fully powering down after software update.
Recalls/TSBs owners mention: No manufacturer response documented. One case noted CPU suspected not shutting down after transmission safety recall software update.
Brake system electrical failure—power loss and limp mode
Electrical fault causes brake system to enter limited-speed mode or lose power assist entirely. Messages display 'Brake System Failure' with max speed 20–62 mph. Actual brake pedal may lose assist or become unresponsive.
When: Multiple instances across different mileages; some under 13,000 miles
Symptoms owners cite: Brake system failure message on dash; Max speed limited to 20–62 mph; Vehicle brakes itself without driver input; Loss of power steering assist; Hard brake pedal or unresponsive brakes; Multiple warning lights (ABS, ESC, power steering) illuminate together
Codes mentioned: Brake failure codes, ABS malfunction, ESC service codes
Repairs/costs cited: Dealer attempts computer recalibration ($200 charge reported). Electronic brake module replacement in some cases. Multiple dealers unable to find cause.
Recalls/TSBs owners mention: 2019 recall exists for identical failures; 2020 models not included. Owners report calling GM recall hotline and being told 2020 is not covered.
Check engine light and multiple warning messages with no codes
Check engine light and service messages (ESC, ABS, reduced engine power, etc.) illuminate but disappear before dealer inspection or no codes are found. Issues recur intermittently.
When: Various mileages; some within weeks of purchase
Symptoms owners cite: Check engine light illuminates then goes off; Vehicle jerks while driving; Multiple dashboard warning messages; Alerts repeat every few minutes even after dismissal; Blinkers blink fast as if bulbs need replacement
Codes mentioned: Check engine codes (clear before diagnosis in some cases)
Repairs/costs cited: Dealers spend 5–7 hours at $150/hour troubleshooting with no resolution. Unknown parts replaced in some cases with no effect. One shop referred to dealership after hours of work yielded nothing.
Recalls/TSBs owners mention: $500 coupon offered in one case instead of repair. Dealer refusal to inspect once light turns off. No root cause identified.
Transmission electrical locking and hard downshift
Transmission locks up momentarily or downshifts hard at various speeds with arching/burning wires underneath passenger side. Chafed wiring contacted transmission system.
When: Various mileages
Symptoms owners cite: Drastic speed drop with transmission unable to shift; Transmission locks up momentarily; 'D' flashes on dashboard; Unable to accelerate after lockup; Burning smell after trips; Hard downshifting at various speeds
Repairs/costs cited: Chafed wire repair. Video evidence taken by GM personnel showing fire/arching but not provided to owner (on official app, unable to download).
Recalls/TSBs owners mention: Dealer states unrelated to rear wheel lockup recall. Confirmed as electrical issue. Dealer notes this is 2nd truck that week with same complaint.
Emissions system failure—P2C7A code and NOx component replacement
ECM and emissions control system malfunction with persistent P2C7A code. NOx catalytic converters and diesel particulate filters replaced repeatedly under warranty but issue persists. Exhaust leak allows exhaust gas into cab.
When: Starting June 2024
Symptoms owners cite: Check engine light and Service Engine Soon light illuminated; Reduced engine performance; Poor fuel economy; Exhaust fumes entering cab; Emissions non-compliance
Codes mentioned: P2C7A
Repairs/costs cited: NOx catalytic converter replacement twice under warranty; diesel particulate filter replacement. Components available for inspection. Issue persists after repairs.
Recalls/TSBs owners mention: Dealership diagnosed multiple times. Dealer blamed fuel quality; fuel distributor refuted this claim. No resolution.
Rear sliding window water intrusion and electrical damage
Rear sliding window leaks water into cab during rain and car washes, causing water to contact electrical modules, causing mold, rust, and component failure. One case flooded entire truck bed and floorboards.
When: From purchase (December 2020) onward
Symptoms owners cite: Water pools inside cab after rain or car wash; Mold growth behind rear seats; Rust under rear seats; Backup camera malfunction after rain; Backup camera stopped working for a day after rain; Entire rear interior soaking wet; Crack in rear window
Repairs/costs cited: Dealers suggest caulking as temporary fix (inappropriate for new vehicle). One case required ~$10,000 in repairs to restore electrical controls. No permanent repair documented.
Recalls/TSBs owners mention: Dealers say this is a common occurrence. No recall or TSB mentioned.
Tailgate latch electrical failure and unwanted release
Tailgate releases itself without switch activation while parked, with trailer attached or when approaching vehicle. Water entry into tailgate fills it like a bucket, suspected to be shorting the electrical switch.
When: From December 2020 purchase onward; multiple occasions
Symptoms owners cite: Tailgate releases on its own while parked; Tailgate releases while trailer attached; Tailgate releases when attaching trailer (striking owner); Tailgate fills with water during rain and car washes; Dent to upper tailgate section; Kicker speaker system damaged and rusted; Tailgate switch malfunction
Repairs/costs cited: Not repaired. Owner suspects water intrusion electrically shorting switch due to tailgate design allowing water pooling.
Recalls/TSBs owners mention: No manufacturer response documented. Heavy Kicker speaker system in tailgate suspected to worsen problem by adding weight and increasing water retention.
Rear sliding glass spontaneous shattering
Rear sliding window shatters without impact or external cause while vehicle is parked. Window fails completely, distributing tempered glass throughout cab interior.
When: Various mileages and ages; one case at approximately 4 years old
Symptoms owners cite: Rear sliding window shatters on its own while parked; No impact or external strike; Tempered glass fragments scattered inside cab; Window failure verified by security camera footage
Repairs/costs cited: Not repaired. Owner attempted to contact GMC service; dealer requested 2–3 day hold without loaner vehicle.
Recalls/TSBs owners mention: No manufacturer response. Dealership unable to provide loaner, preventing owner from leaving vehicle for inspection.
Backup camera display—excessive brightness and glare
Backup camera display is dangerously bright at night, creating glare on rear window that blocks visibility and makes safe backing impossible. Display is also blurry at night.
When: Normal use, nighttime backing
Symptoms owners cite: Display brightness excessive at night; Glare thrown onto rear window; Inability to see out rear window while backing; Side view mirrors unusable due to glare; Blurry image at night; Owner resorts to opening driver door to back safely
Repairs/costs cited: Dealer states no fix available even though issue is widespread online. No adjustment possible.
Recalls/TSBs owners mention: No remedy found despite multiple complaints online. Dealer claims unfamiliar with issue despite documented prevalence.
Infotainment and backup camera display malfunction
Backup camera and infotainment display go blank during operation, flash different colors, or become unusable. One case occurred while owner was backing up.
When: During normal use
Symptoms owners cite: Display goes completely blank; Screen flashes different colors; Flashing colors prevent use; Failure occurs during backup (safety hazard)
Repairs/costs cited: Not repaired in all cases reported. No repair cost noted.
Recalls/TSBs owners mention: No manufacturer response documented.
Blind spot sensor false alarms and malfunction
Side view mirror blind spot sensors engage and alert driver to obstacles that are not present. Sensor remains dirty or defective even after washing vehicle.
When: Early ownership; one case at 400 miles
Symptoms owners cite: Blind spot alert engages with no vehicle nearby; Alert engages on both sides simultaneously; Sensor reads as dirty after car wash; Malfunction recurs after washing vehicle
Repairs/costs cited: Not repaired. Owner washed vehicle without resolution.
Recalls/TSBs owners mention: Dealer blamed dirty sensors; no repair attempted after washing did not resolve issue.
Adaptive cruise control malfunction and unexpected deceleration
Adaptive cruise control disengages or decreases speed without vehicle or obstacle present. Cruise icon changes color and truck slows with no visual warning or detection indicator on dash.
When: December 2020 and April 2021 reported
Symptoms owners cite: Cruise control disengages at highway speed (60 mph); Truck slows suddenly with no vehicle in front; No vehicle within quarter mile front or back; No debris visible on road; Cruise icon changes from orange flash to blue color; No orange warning icons illuminate as normal
Repairs/costs cited: Reported to dealership and filed; no codes appear when customer service attempts to pull them.
Recalls/TSBs owners mention: Dealership filed report; diagnostic attempt showed nothing wrong.
Seat vibration from front left sensor false alarm
Front left sensor continuously vibrates driver's seat and illuminates red warning light indicating obstacle near left front. Occurs after rain, car wash, or oil change.
When: After rain, car wash, or oil change
Symptoms owners cite: Driver's seat vibration from sensor false alarm; Red light warning illuminated continuously; Alarm indicates obstacle near left front; Recurs on multiple occasions
Repairs/costs cited: Not repaired. Issues stop after a period of time on their own in some cases.
Recalls/TSBs owners mention: Reported to dealership twice (December 2020 and April 2021); noted in file.
Voltmeter erratic fluctuation after software update
Volt gauge jumps back and forth between white lines, slowly rising to max then dropping to lower limit in continuous cycle. Owner concerned of electrical failure. Dealership claims this is normal operation.
When: After repair (transmission safety recall software update)
Symptoms owners cite: Volt meter needle jumps between white lines; Slow rise to max line followed by slow drop to lower limit; Continuous cycling of gauge; Owner concerned electrical failure imminent
Repairs/costs cited: No repair attempted. Dealership maintenance tech stated this is designed operation within GM parameters.
Recalls/TSBs owners mention: GM stance per maintenance tech: operating within tolerance and parameters.
Auto start-stop CPU not powering down after software update
After transmission safety recall software update, CPU fails to fully power down, causing battery to drain rapidly even when vehicle is off.
When: After software update for transmission safety recall
Symptoms owners cite: Battery completely dead after week of sitting; No accessories on, new battery (6 months old); Multiple jump starts required; 3+ hours of run time needed to charge battery enough to start on own; Battery tested fine and is charging
Repairs/costs cited: No permanent repair documented. Owner suspects CPU never fully powered down after software update.
Recalls/TSBs owners mention: No response. Owner concerned about safety risk with auto-start function if battery cannot hold charge at intersection.
Multiple warning codes after low-voltage event
After battery goes dead and is recharged, vehicle displays 14 different error codes that are lost with low voltage event. These codes reset after recharge.
When: After battery drain event
Symptoms owners cite: Vehicle would not go into gear after jump start; All warning lights and codes present; Codes clear after extended sitting and recharge
Codes mentioned: 14 different codes (not specified; lost with low voltage)
Repairs/costs cited: No repair needed after codes cleared. Vehicle operated normally after recharge.
Recalls/TSBs owners mention: No response.
Safety Restraint System intermittent alerts
Intermittent 'Service Safety Restraint System' alerts appear while driving on vehicle with minimal miles.
When: 550 miles on odometer
Symptoms owners cite: Service Safety Restraint System alerts (intermittent); Alerts appear while driving
Repairs/costs cited: Not repaired. Dealer stated unable to trace intermittent issue.
Recalls/TSBs owners mention: Dealer advised issue cannot be traced unless warning light remains on continuously.
Brake light illumination electrical fault
Electrical malfunction causes brake light illumination fault code, likely responsible for battery drain when vehicle is off.
When: Multiple instances
Symptoms owners cite: Check engine codes read 'problem with brake light illumination'; Battery drained while no lights or devices left on
Codes mentioned: Brake light illumination fault
Repairs/costs cited: No specific repair documented.
Recalls/TSBs owners mention: No response.
Power steering electrical failure
Power steering works intermittently or stops working completely. One case linked to wiring harness chafing.
When: Various mileages
Symptoms owners cite: Power steering works sometimes then stops; Loss of power steering at highway speed; Reduced steering assist
Codes mentioned: Service Power Steering code
Repairs/costs cited: Wiring harness repair in chafing cases; no cost cited.
Recalls/TSBs owners mention: No response documented.
Trailer brake system electrical malfunction
Trailer brake system electrical function fails or malfunctions.
When: Unspecified
Symptoms owners cite: Trailer brake system failure
Repairs/costs cited: Not repaired.
Recalls/TSBs owners mention: No response documented.
Auto start-stop cannot be permanently disabled
Auto start-stop feature cannot be permanently disabled. Owner must push button each time engine is started. Some GM vehicles allow permanent disabling via settings.
When: Ongoing since purchase
Symptoms owners cite: Auto start-stop engages every startup; No option to permanently disable; Manual button press required each startup
Repairs/costs cited: No fix available. Owner requests firmware upgrade to ECM to allow permanent disabling.
Recalls/TSBs owners mention: No firmware upgrade or response documented; other owners complained with no GM response.
Lighting and electrical component failure
Interior lights, headlights, and radio fail to shut off, draining battery.
When: Early ownership
Symptoms owners cite: Interior lights stay on; Headlights stay on; Radio stays on; Battery drained overnight; Vehicle will not start
Repairs/costs cited: Not repaired; owner called GM roadside assistance.
Recalls/TSBs owners mention: No response.
Backup camera always-on malfunction
Backup camera feed remains displayed on dashboard even while vehicle is being driven at highway speed.
When: Normal operation
Symptoms owners cite: Camera display always on, even during highway driving; Cannot disable camera feed
Repairs/costs cited: Not repaired.
Recalls/TSBs owners mention: No response documented.
Synthesized from 50 NHTSA owner complaints — unverified consumer allegations, summarized for patterns. The verbatim filings appear below.
What owners are reporting 4 most recent
The morning of December 12th, 2025 I used my vehicle to transport my daughter approximately 5 miles round trip from our home to drop her off at daycare and then I returned home. I used my front and rear defrost elements to expedite removal of heavy condensation which had formed on all windows overnight. This was approximately 7 AM. I parked my truck in the driveway and went inside until…
After having all sorts of warnings over time like "service ESC," "service parking brake," and more, I now see "brake system failure: 62 MPH top speed" flash across my dash. I am reading and hearing that this is a very dangerous problem. New truck. Brand new. Had it less than a year. Brake message always on start up.
The contact owned a 2020 GMC Sierra 1500. The contact stated that after the vehicle was purchased and while driving at an undisclosed speed, the check engine warning light illuminated. The dealer was contacted. However, the check engine light turned off, and the dealer refused to inspect the vehicle. The contact stated that while driving at an undisclosed speed, the vehicle jerked and the check…
Had electrical trouble with your 2020 GMC Sierra?
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 2020 GMC Sierra?
It's a meaningful issue. 50 complaints have been filed and the failure mode causes operational problems for owners. Repairs average $850.
At what mileage does the electrical typically fail?
Across the 8 complaints that reported odometer mileage, most electrical failures cluster between 6,400 and 80,000 miles, with the median around 15,000. A quarter of owners report trouble before 6,400; a quarter make it past 80,000. Maintenance history matters more than the odometer alone — this is the reported failure window, not a guarantee.
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/2020/GMC/Sierra.
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.