I purchased my 2018 GMC Sierra 1500 pickup truck new in 2018. To date it only has 28K miles on it. I have never used the trailer breaking system that it came equipped with. On 12/24/22 we were traveling to a family function for Christmas. The "service trailer break system" warning message came on and the chime chimed continuously until I got to my destination, about an hour away. This chime was…
2018 GMC Sierra electrical problems
moderate 30 complaints filed with NHTSA · avg repair $850 · see electrical across all vehicles →
Complaints
30
Recalls
0
Avg fix
$850
1fire
What stands out
Owners have filed 30 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 3 years — the issue may be aging out of the active population.
The failure pattern owners describe
Owners report a broad range of electrical problems on 2018 GMC Sierras, with trailer brake system warnings being the most common complaint. The "service trailer brake system" alert appears constantly on many vehicles—sometimes lasting an hour of non-stop beeping that can't be silenced—despite no actual brake malfunction. Dealers have replaced chassis control modules and wiring harnesses at considerable expense ($1,191–$1,600 per repair), and the problem appears so widespread among GM trucks that multiple owners expect a recall.
More serious: several owners lost critical power while driving. One reported complete brake failure and steering lockup at 35 mph at an intersection; another experienced intermittent stalling at highway speeds with warning lights that dealers couldn't diagnose. Brake problems beyond false warnings include lock-up on one side causing unsafe swerving, increased pedal effort, and extended stopping distance—all reported as daily hazards.
Electrical system failures show up as battery drain (one truck dead after 5 days unused; replaced three times in succession), wiring harness damage from rodent attacks through soy-based coatings, wiring separation causing no-start, and harness pinch-points at door hinges. One 2018 Sierra caught fire while parked in a driveway seven hours after a short drive, burning completely and damaging the owner's house. Another owner reports the truck locking itself with the engine running and phantom window movements.
Infotainment glitches, spontaneous instrument cluster changes, and dashboard display failures add distraction during driving. Service visits often fail to find root causes, leaving owners unrepaired or needing multiple visits."
Same GMC Sierra electrical reports on nearby years: 2015 · 2017 · 2019 · 2020 · 2021
Failure modes owners describe
Vehicle fire while parked
Vehicle caught fire approximately 7 hours after last drive while parked in driveway. Fire started at rear of vehicle around license plate and bumper area, progressed through bed cap, then to cab interior. Fuel tank ruptured during fire. Caused total loss of vehicle and collateral damage to house and driveway.
When: After 5-minute drive earlier same day; fire occurred ~7 hours later with vehicle parked
Symptoms owners cite: Vehicle fire originating at rear bumper/license plate area; Fire progression through fiberglass bed cap; Fuel tank rupture; Total vehicle loss
Undersized battery cables with factory towing package
Factory-installed battery cables were undersized for the trailer brake modulator on 2018 GMC Sierra with towing package. Insufficient voltage delivery caused inconsistent trailer brake function despite brake system otherwise functioning.
When: Problem noticed in 2021 RV season after purchase; 7,500 lb RV trailer
Symptoms owners cite: Inconsistent electric trailer brake function; Random "Check Trailer Wiring" dashboard warnings; Intermittent brake failures on towed trailer; Unpredictable warning patterns
Repairs/costs cited: Dealer replaced with properly sized battery cables; cost $1,600
Service trailer brake system warning light and chime malfunction
Continuous "service trailer brake system" warning light and chime that cannot be disabled. Occurs without actual trailer brake system problem. Owner had never used trailer braking system. Diagnostic confirmed trailer brake switch functioning properly but chassis control module suspected as culprit.
When: At 28,000 miles; occurred 12/24/22
Symptoms owners cite: Continuous, non-stoppable warning chime; "Service trailer brake system" warning light; Distraction from driving; Unable to silence alert
Repairs/costs cited: Chassis control module replaced and reprogrammed by factory technician; cost $1,191.86
Trailer brake system false warnings and repeated service visits
Constant "service trailer brake system" alert with audible beeping covering speedometer display. Beeping restarts when dismissed. Problem persists across multiple dealer visits and owner attempts at repairs using factory parts mentioned online. Multiple complaints indicate this is a widespread known issue among GM vehicles.
When: Various instances reported; one vehicle just purchased
Symptoms owners cite: Constant "service trailer brake system" alerts; Loud, repetitive beeping at 30-second intervals; Alert pops up and restarts after dismissal; Alert covers digital speedometer; Occurs at any speed including when stopped
Repairs/costs cited: Multiple GM service center visits required; several hundred dollars per repair; owners report online that other GM owners have experienced same issue
Loss of electrical power—brakes and steering lock up while driving
Complete loss of brake power and steering lock-up while driving at 35 mph at intersection. Lights and stereo remained on. Check engine light illuminated. Vehicle would not restart initially (no clicking sounds), then restarted after 30 minutes with red check engine light. Towed to dealer.
When: Early morning hours while actively driving
Symptoms owners cite: Total brake power loss; Steering wheel lock-up; Red check engine light; Intermittent yellow flickering check engine light; No starter response initially; Dimmed lights during restart attempt
Codes mentioned: Check engine light (code not specified)
Repairs/costs cited: Towed to dealer; repair details not provided
Repeated battery failures
Multiple battery replacements required within short timeframe. First battery replaced one month after purchase; second battery replaced three weeks later; third battery replaced one day after second replacement. Failure not duplicated at dealer; VIN not associated with any recall.
When: Early in ownership; at approximately 36,000 miles total failure occurred
Symptoms owners cite: Battery failure requiring replacement; Repeated rapid battery failures; Multiple replacements in succession
Repairs/costs cited: Three battery replacements; dealer unable to duplicate failure
Battery drain leading to dead battery after short non-use periods
Battery dies after 5 days of vehicle not being driven. Problem is recurring. Dealer states nothing is wrong and made no repairs. Owner stranded multiple times.
When: After 5 days of vehicle sitting
Symptoms owners cite: Battery drain when vehicle unused for 5 days; Recurring dead battery condition; Vehicle stranded multiple times
Repairs/costs cited: No repairs made; dealer found no issue
Wiring harness damage from rodent infestation—soy-based wire coating
Wiring harness eaten and destroyed by squirrels due to soy-based wire coatings used by GMC approximately 10 years ago. Entire electrical system compromised, particularly safety systems. Multiple warning lights and in-dash messages displayed (approximately 10).
When: Unknown timing; ongoing issue after damage discovery
Symptoms owners cite: Wiring harness eaten by rodents; Compromised entire electrical system; Non-functional airbags; Windows inoperable; Door locks stuck open or closed without physical key; StabiliTrak system shutting off arbitrarily; Windshield wipers working intermittently; Approximately 10 in-dash warning messages; Multiple warning lights activated
Repairs/costs cited: Main harness repaired at dealership (paid by insurance); dealership identified additional portions of electrical system still needing repair
Wiring harness separation and wire arcing causing no-start condition
Main harness under truck from front to back separated from conduit, exposing wires that were arcing. Truck would not start until harness repaired. Owner states truck too young for this type of problem.
When: Unknown mileage/timing
Symptoms owners cite: Wiring harness separation from conduit; Exposed wires arcing; No-start condition
Repairs/costs cited: Harness repair completed; owner reports high cost for repair
Harness pinch point damage at door hinge—rear sliding window
Harness routed from center console through driver-side door hinge was sheared, cutting all 3 wires in half at pinch point. Caused rear sliding window failure and other functions to fail. Fuse 2 investigation initially appeared responsible but was not root cause. Owner spliced wires as temporary fix. Owner identifies fire hazard risk.
When: Unknown timing
Symptoms owners cite: Rear sliding window non-functional; Fuse 2 blown; Multiple functions controlled by that harness non-functional; Fire hazard from exposed/arcing wires
Repairs/costs cited: Wires spliced as temporary fix; owner recommends factory reroute or corrugation protection
Service trailer brake system warning with unknown underlying cause
Service trailer brake system warning light illuminated at highway speeds. Vehicle taken to dealer where wiring harness replacement was recommended but not performed. Cause of failure not confirmed.
When: At approximately 77,000 miles
Symptoms owners cite: Trailer wiring harness system warning message illuminated at highway speeds
Repairs/costs cited: Dealer recommended wiring harness replacement but did not perform repair
Intermittent stalling while driving on highway
Vehicle occasionally shuts off while driving at various highway speeds. Multiple unknown warning lights illuminated when stalling occurs. Vehicle can be restarted and driven again. Cause of failure not identified by dealer diagnostic.
When: At approximately 128,000 miles
Symptoms owners cite: Vehicle shuts off while driving; Multiple unknown warning lights; Intermittent occurrence at various speeds; Successful restart after stalling
Repairs/costs cited: Dealer diagnostic performed but cause not found; owner advised to return if failure recurs
Recalls/TSBs owners mention: Manufacturer notified
Brake lock-up causing unsafe swerve and loss of directional control
Brakes sometimes lock up or fail to disengage on one side, causing truck to swerve into next lane requiring steering correction. ABS system suspected as cause due to speed sensor misinformation. Occurs on average 1-2 times daily, extremely dangerous at highway speeds.
When: Recurring; 1-2 times daily on average
Symptoms owners cite: Brake lock-up or failure to disengage on one side; Truck swerves to right requiring overcorrection; Audible brake squeal; Requires exiting freeway to wait 5-10 minutes for issue to stop; Occurs at 75 mph highway speeds
Repairs/costs cited: Possible causes cited by owner: brake calipers, hoses, speed sensors sending wrong information to ABS system
Increased brake pedal effort and extended stopping distance
Hard brake pedal requiring increased effort with potentially extended stopping distance. Condition most prevalent at low speed with soft brake application. Service brake assist alert activates on Driver Information Center. Owner reports extreme safety risk with children in vehicle.
When: Unknown timing
Symptoms owners cite: Increased brake pedal effort; Hard brake pedal; Potentially increased stopping distance; Most prevalent at low speed with soft braking; "Service brake assist" alert activation
Repairs/costs cited: Owner cites Technical Service Bulletins N182202780 & NT192268490 as relevant but notes they need to be tied to specific VIN
Spontaneous door locking with engine running
Truck locked itself with engine running while parked in driveway without owner input. Also experienced brake engagement preventing vehicle movement while in gear (drive or reverse positions).
When: Unknown timing; occurred while parked
Symptoms owners cite: Spontaneous door lock engagement with engine running; Brake or similar system preventing movement in drive or reverse; Back driver-side window rolling down partially without initiation
Multiple electrical warning lights at purchase—new vehicle
Vehicle purchased in 2021 and within 2 weeks displayed multiple warning lights for service StabiliTrak, trailer brake system, and ABS. Also received code U0510 for active grille shutter assembly. Owner reports these are very common and unsafe issues.
When: 2 weeks after 2021 purchase
Symptoms owners cite: Service StabiliTrak warning; Service trailer brake system warning; ABS light illumination; Code U0510 active grille shutter assembly
Codes mentioned: U0510
Loss of dash electrical system with multiple warning resets
Complete loss of dashboard electrical system. When power restored, service StabiliTrak, service suspension, and other warning lights activated. Headlights flicker and engine powers down intermittently before restarting automatically. All warnings clear when suspension fuse is pulled or negative battery terminal removed and replaced.
When: Unknown timing
Symptoms owners cite: Loss of dash electrical system; Service StabiliTrak warning after power restoration; Service suspension warning light; Flickering headlights; Engine powering down and restarting intermittently; Multiple warning light activation
Repairs/costs cited: Warnings clear with suspension fuse removal or negative battery terminal disconnect/reconnect
Multiple warning lights and sensor-related failures
Vehicle displayed warning lights for ABS, traction control, trailer brakes, and front park assist. Speed control/cruise control did not function. Presented safety issue. Dealer repaired by replacing left rear wheel speed sensor.
When: Unknown timing
Symptoms owners cite: ABS warning light; Traction control warning; Trailer brake warning; Front park assist warning; Speed control/cruise control inoperable
Repairs/costs cited: Left rear wheel speed sensor replaced; cost approximately $216
Infotainment system phantom changes and software glitches
Instrument system and cluster/panel display change spontaneously without owner input. Phantom changes to all functions creating major driving distraction and safety hazard. Dealership attempted software update without success.
When: Unknown timing
Symptoms owners cite: Spontaneous instrument cluster changes without input; Phantom menu/setting changes; System distraction from driving attention; Software malfunction despite update attempts
Repairs/costs cited: Dealership attempted software update; issue persisted
Brake system noise and control warning lights
Brake system producing scratching noises suggesting caliper or caliper piston problems. Trailer brake system light and traction control light activating simultaneously.
When: Unknown timing
Symptoms owners cite: Scratching noises from brakes; Trailer brake system warning light; Traction control warning light; Suspected caliper or piston issue
Rear sliding window defogger fire hazard
Rear sliding window defogger element started smoking and filled cab with smoke, creating immediate fire hazard to occupants.
When: Unknown timing
Symptoms owners cite: Defogger element smoking; Smoke filling cab; Potential fire hazard
Towing control module failure
OEM Towing Control Module (Part # 23337305) failed. Replaced with factory part but replacement unit failed again within 60 days.
When: 60 days after replacement
Symptoms owners cite: Towing control module malfunction; Repeated failure of replacement part
Repairs/costs cited: Replaced with OEM factory part; part failed again within 60 days
Dashboard display darkness and collision warning malfunction
Dashboard display goes dark with collision alert warning appearing. Tires reportedly spin out of control when turning or driving normally despite adequate tread depth remaining. Owner suspects tire-related cause but correlation unclear.
When: Unknown timing
Symptoms owners cite: Dashboard display goes dark; Collision alert warning displays; Tires spin out of control when turning; Tires spin during normal driving; Issue despite adequate tire tread
Vehicle behavior alterations and loss of control sensation—unverified claims
Owner alleges vehicle steers itself left or right while driving and brakes remain constantly engaged with varying pressure. Vehicle returned to dealership 15+ times with 35+ days out of service. GM engineer/technician inspection found no cause. Infotainment system shows multiple glitches. Owner characterizes behavior as vehicle being hacked and controllable by others. Vehicle undergoing GM replacement due to issues. Owner reports extensive video and photographic documentation.
When: Recurring issue during owner's operation
Symptoms owners cite: Steering wheel moving without input; Brakes constantly engaged while driving; Variable brake pressure; Infotainment system glitches; Issue occurs only when owner driving (per owner claim); Issue can turn on/off instantly (per owner claim)
Repairs/costs cited: Vehicle brought to dealership 15+ times; 35+ days out of service; GM engineer/technician inspection unable to identify cause; GM issuing vehicle replacement
Recalls/TSBs owners mention: GM engineer/technician inspected vehicle; GM replacement in progress
Synthesized from 30 NHTSA owner complaints — unverified consumer allegations, summarized for patterns. The verbatim filings appear below.
What owners are reporting 2 most recent
My vehicle is hacked anytime I am driving the vehicle I am not in full control. The vehicle steers itself left or right while driving, the brakes are always on while driving sometimes braking harder but always on. The infotainment system has many glitches. This vehicle has been back to the dealership more than 15 times has been out of service over 35 days gm even flew a engineer/tech to inspect…
Had electrical trouble with your 2018 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 2018 GMC Sierra?
It's a documented issue but not catastrophic. 30 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 30 complaints filed, electrical issues most often appear around 98,911 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/2018/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.