The Intermediate speed sensor 2 and internal transmission harness failed. The repair was to replace the internal transmission harness and intermediate speed sensor. This vehicle is a 2021 and I was told this was recalled on a 2022 only.
2021 GMC Sierra electrical problems
severe 50 complaints filed with NHTSA · avg repair $850 · see electrical across all vehicles →
Complaints
50
Recalls
0
Avg fix
$850
3fires
When does it fail?
Of the 50 electrical complaints filed for the 2021 GMC Sierra, 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
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.
The failure pattern owners describe
Owners of 2021 GMC Sierras report a broad spectrum of electrical failures that range from inconvenient to dangerous. Battery drain is a recurring theme: multiple owners describe complete overnight discharge despite new batteries and passing alternator tests, with some smelling burning plastic or wire insulation when opening the hood. Wiring harness chafing is another major complaint, causing transmission hesitation, harsh shifts, stalling on the highway, and repeated limp-mode conditions. Repair costs exceed $5,000 to $8,100, and owners note that GM is aware of the design flaw yet refuses warranty coverage once mileage exceeds the threshold.
Engine bay fires represent the most serious failure: two owners report flames erupting while the truck sat parked in a driveway, with fire investigators citing brake controller defects and moisture-exposed manufacturing issues. In both cases, GM refused assistance despite confirmed manufacturing fault.
Infotainment systems fail after automatic OTA updates that owners cannot decline, disabling GPS, Bluetooth, backup cameras, and speedometer readouts. The multi-function tailgate opens repeatedly while driving, posing hazards to other motorists. Intermittent electrical issues appear after dealer engine-recall repairs, leaving vehicles unable to start for 24 hours if powered down while warning lights are active. Dealers have consistently failed to diagnose or repair these problems.
Same GMC Sierra electrical reports on nearby years: 2018 · 2019 · 2020 · 2022 · 2023
Failure modes owners describe
Battery drain / parasitic draw
Battery discharges completely overnight or after sitting idle for a few days, with no warning lights. Multiple owners report needing jump starts or battery replacement within weeks of purchase or occurrence.
When: 10,126 miles (first narrative); 41k miles used purchase (second narrative); occurring after sitting 2-3 days (narrative #38)
Symptoms owners cite: Complete battery discharge overnight; Battery dies after sitting 2-3 days; Burned wire/plastic smell from engine bay when opened after discharge; Check engine light intermittent, comes on then goes off; No warning lights before discharge
Repairs/costs cited: Battery replaced at 10,126 miles; battery and alternator tested—both normal; no root cause found after hours of diagnostics at multiple shops
Recalls/TSBs owners mention: GM Canada referred owner to GM USA; no response from GM USA; dealership could not identify issue after 3+ hours diagnostic time
Wiring harness chafing / internal transmission harness failure
Damaged or chafed wiring causes hesitation, shaking, harsh gear engagement, limp mode, stalling while driving, and difficulty restarting. Some owners report replacement costs of $5,000–$8,100. Known issue GM is aware of per owner reports.
When: First incident within 6 months of ownership (narrative #10); 60,129 miles (narrative #18); after transmission recall service (narratives #14, #33); intermediate speed sensor 2 failure at unspecified mileage (narrative #40)
Symptoms owners cite: Transmission hesitation and harsh gear engagement; Vehicle lunges and shakes violently; Engine shuts off while driving on interstate; Vehicle goes in and out of limp mode; Transmission slams into gear, rear wheels lock up; Rear wheels locked up while driving; Vehicle fails to restart after stalling
Codes mentioned: Limp mode (multiple narratives)
Repairs/costs cited: Wiring harness replaced ($5,000–$8,100 depending on dealer); wire chafing taped and rerouted at one dealer but problem recurred; intermediate transmission harness and speed sensor replaced; one owner reports harness repair occurred on 2022 as recall but not 2021
Recalls/TSBs owners mention: GM has work orders out with codes and symptoms but owner reports GM 'won't do anything about it'; some warranty denial due to mileage; owner states they are out of warranty at time of repair
Engine fire / electrical fire in engine compartment
Fire ignites in engine compartment while vehicle parked in driveway, unrelated to driving. Fire starts near battery and back of engine compartment. One case confirmed as brake controller defect; another case mentioned parts left outdoors and exposed to moisture during manufacturing.
When: After parking in driveway, within minutes of owner returning home; no warning before fire
Symptoms owners cite: Smoke rolling out from under hood; Visible flames from back of hood; Fire in engine bay within 5 minutes of initial smoke; Intense heat destroying entire engine and cab; No warning lights or alerts prior to fire
Repairs/costs cited: Fire investigators determined one case was brake controller defect; another mentioned manufacturing defect (parts exposed to moisture during assembly); totaled vehicles; insurance paid out at lowball amount
Recalls/TSBs owners mention: GM refused to help with either case; one owner reports GM said they had active insurance claim so would not assist; manufacturer stated it was their defect but refused assistance
Transmission slipping / loss of propulsion (L87 engine recall failure)
Transmission slips or engine fails under load (on inclines or during acceleration), causing loss of propulsion. One confirmed recall failure (N252494003) for L87 engine; owner reports dealer denied courtesy transportation despite confirmed failure and recall procedures requiring it.
When: At 50–65 MPH on incline (narrative #11); September 29, 2025 confirmed failure of recall N252494003 (narrative #3); high RPM, hesitation, reduced power noted
Symptoms owners cite: Transmission slips or misfire on incline; Engine fails under acceleration; Loss of propulsion; Check engine light illuminated; Vehicle enters limp mode; Multiple warning lights on dash
Codes mentioned: Limp mode (N252494003 recall symptom), Check engine light
Repairs/costs cited: Replacement engine delayed under GM National Control up to 3 months (per GM bulletin); one owner at 75,000 miles not covered due to VIN not in recall campaign
Recalls/TSBs owners mention: GM Recall N252494003 issued for L87 engine loss of propulsion; GM Bulletin DCS7222 allows courtesy transportation during recall; dealer refused to provide loaner or rental despite GM policy and confirmed failure; owner reports GM FAQ N252494002 states courtesy transportation IS available for this recall
Engine coolant flow control valve position sensor failure (P2B60)
Coolant flow control valve (AC Delco part #55516369) fails intermittently, causing severe power loss or erratic performance. Check engine light comes on sporadically. Known issue per dealer but no recall issued. Part on backorder with no release date.
When: Symptoms began December 2023, sporadic then constant after that; less than 300 miles on vehicle for one owner (narrative #26); occurring at time of writing for another (narrative #15)
Symptoms owners cite: Check engine light comes on sometimes but not always; Unpredictable power loss—truck barely pulls itself; Power loss occurs same trip without shutting ignition off; Severe decrease in fuel economy; Warning of reduction in engine power
Codes mentioned: P2B60
Repairs/costs cited: Part AC Delco #55516369 still installed on vehicle; part on backorder for 3+ months with no release date; dealer aware but no recall issued
Recalls/TSBs owners mention: Dealer confirmed known issue; no recall; part on backorder indefinitely
Infotainment / radio system failure from OTA update
Over-the-air (OTA) update fails and leaves infotainment system inoperable. Radio, GPS, Bluetooth calling, and backup camera disabled. Owner receives update automatically without consent and no option to decline. Dealer denies warranty coverage despite vehicle under warranty.
When: Automatic OTA update occurred at approximately 10,450 miles (narrative #12); 52,000 miles for narrative #23; less than 300 miles on vehicle for narrative #39
Symptoms owners cite: Screen displays 'Update failed, return to dealer'; Radio/information system completely inoperable; Bluetooth calling capability lost; GPS and turn-by-turn navigation fail; Backup camera inoperable; Speedometer obstructed, digital speedometer fails; Dashboard gauges and instrument cluster malfunction; Unknown notifications flash on panel; System reboots randomly while driving
Repairs/costs cited: System reboot at dealer temporarily resolved one case but failure recurred; repair cost $1,300+ for one owner out of warranty; another owner paid for radio module replacement burned out by failed update
Recalls/TSBs owners mention: GM pushing updates without owner consent; dealer called non-warrantable repair and 'wear and tear' despite vehicle under warranty; GM offered only 'rewards points' in one case; GM has active recall N202319250 for same issue on 2021 GMC Tahoe but not Sierra; no fix provided at second dealership consulted; no additional assistance from manufacturer
Multi-function tailgate opening unintentionally while driving
Tailgate releases and opens while vehicle is driving or parked, creating hazard of items becoming projectiles. Problem occurs intermittently after water intrusion or moisture exposure (car wash, rain). Multiple owners report same issue recalled in Canada and on HD models but not on 2021 Sierra 1/2 ton in US.
When: Began 1.5 years ago for one owner; after car wash for another (narrative #29); in heavy rain or after truck wash (narrative #25); intermittent across various narratives; 57,000 miles for narrative #32
Symptoms owners cite: Tailgate opens unintentionally while driving; Tailgate opens when parked; Tailgate immediately opens again after latching; Tailgate drops when wet (heavy rain, car wash); Inner tailgate releases outer tailgate; Constant clicking of electric switch; Tailgate opens when hitting bumps; Damage to hitch from opening; Warning light 'inner tailgate open' displayed
Repairs/costs cited: Rear control replaced at dealer—worked 4–5 months then failed again; replaced 3 times by GM with ongoing issues; owner paid for replacement on one case because VIN not in recall campaign; scratched paint from repeated opening/closing
Recalls/TSBs owners mention: Recall N232426401 exists but one owner's VIN not included in campaign; recalled on 2500 HD and Canadian 1/2 ton models but not US 1/2 ton; problem recognized by manufacturer and dealer but not addressed uniformly; no repair performed for some owners
Infotainment screen / instrument cluster malfunction and blackout
Dashboard display, speedometer, radio screen, or instrument cluster goes blank, reboots, or becomes inoperable during driving or at startup. Problem occurs randomly and intermittently.
When: At startup with loud cranking sound (narrative #22, 100 miles); during driving while using GPS (narrative #12, 10,450 miles); randomly while driving (narratives #27, #37, #44)
Symptoms owners cite: Dashboard gauges and infotainment center malfunction; Instrument cluster inoperable; Radio screen goes blank randomly; Can hear radio but cannot see screen; Digital speedometer fails to operate; Screen sporadically goes blank while using GPS; DIC and touch screen shutdown and restart like rebooting; Loss of mph, gauges, navigation on dash; Console radio dash goes completely black; Loud cranking sound from engine compartment at startup
Repairs/costs cited: System reboot attempted at dealer; failure persisted; cause of failure not determined at dealership; problem intermittent making diagnosis difficult
Recalls/TSBs owners mention: Dealer unable to determine cause; manufacturer notified but no assistance provided; no updates required when checked
Shark fin antenna failure / water intrusion through roof
Shark fin antenna assembly becomes loose, leaks water, and is not properly sealed to body. Water leaks through ceiling/roof into interior. Replacement and installation cost $766.95 at dealership.
When: At approximately 4 years old (truck barely 4 years old per owner)
Symptoms owners cite: Antenna comes loose on its own; Antenna starts leaking water; Antenna wobbly and no longer sealed to truck body; Water leaking throughout ceiling/roof; Interior drench with rainwater
Repairs/costs cited: Shark fin antenna replaced and installed at cost of $766.95; had to return second time because antenna not properly sealed after first repair, causing interior water damage
Recalls/TSBs owners mention: GMC Customer Care refused to refund or help with repair cost; extended warranty (Assure Guard) refused to cover antenna repair; no manufacturer assistance
Trailer brake electrical failure / check trailer wiring error
Trailer brake connection fails intermittently while towing, causing loss of trailer braking. Error message 'Check Trailer Wiring' appears on display but no suggested fix provided. Brakes may reengage abruptly with high gain, requiring hard application of vehicle brakes to compensate.
When: While towing on Interstate 95 in New Hampshire (narrative #17)
Symptoms owners cite: Dashboard displays 'Check Trailer Wiring' error; All brake function to trailer lost when error appears; Connection intermittent—brakes reengage momentarily then disengage; Error codes and symptoms identified by dealer but no fix suggested; Brakes jam with high gain when they suddenly reengage
Codes mentioned: 'Check Trailer Wiring' error code
Repairs/costs cited: Error codes identified by dealership but no suggested repair provided; problem remains unresolved
Recalls/TSBs owners mention: GMC dealership identified error codes but provided no fix
Shift-to-park warning error preventing ignition shutoff
Vehicle displays 'Shift to Park' warning even though transmission is already in Park, preventing immediate ignition shutoff. More frequent in cold weather, suggesting temperature-sensitive fault. Known issue across multiple GM vehicles per owner research; GM has issued recalls for same issue on other models but not Sierra.
When: When attempting to shut off vehicle; more frequent in cold weather
Symptoms owners cite: 'Shift to Park' warning displays despite vehicle in Park; Warning prevents turning off ignition immediately; Doors unlock normally, confirming truck is in Park; Warning disappears after a few seconds, allowing shutdown; More frequent in cold weather
Repairs/costs cited: No repairs performed; owner suspects faulty micro switch or wiring harness in shifter assembly based on research
Recalls/TSBs owners mention: No recall issued for Sierra; owner states problem is known issue across multiple GM vehicles; GM has recalls for same issue on other models
Electrical wiring damage from rodent chewing
Rodents chew through wiring insulation (made of soy-based materials) causing electrical failures. Vehicle fails to start with multiple warning lights illuminated.
When: At approximately 23,300 miles
Symptoms owners cite: Vehicle fails to start; Service parking brake warning light illuminated; Check engine light illuminated; Other unknown warning lights illuminated
Repairs/costs cited: Wiring repaired 3 times for same failure due to rodent damage; soy-based insulation material mentioned as contributing factor
Recalls/TSBs owners mention: Manufacturer notified of failure
Auto start/stop system dangerous delay
Auto start/stop feature causes dangerous delay when restarting at traffic stops. No permanent disable option available. Owner reports near-misses due to hesitation when pulling into traffic.
When: During normal driving when pulling into traffic from stop
Symptoms owners cite: Significant delay for vehicle to restart and move forward; Dangerous delay when pulling into traffic from stop; No way to permanently disable feature
Repairs/costs cited: No repair noted; feature cannot be permanently disabled
Recalls/TSBs owners mention: No response from manufacturer; feature remains in vehicle
Intermittent electrical issues and no-start condition post-engine-recall
Following engine recall repair, truck develops intermittent warning lights that flash on/off (service 4WD, loss traction control, etc.). If ignition turned off while lights are on, vehicle will not start for about 24 hours. Vehicle also experiences random no-start conditions that resolve after a few days.
When: After engine recall remedy in 2025 (narrative #16); random occurrence
Symptoms owners cite: Warning lights (service 4WD, loss traction control) turn on/off intermittently while driving; Vehicle won't start for ~24 hours if shut off while warning lights are on; Random no-start condition—truck doesn't start, then starts after few days; New scraping/squealing sound when backing up (possibly universal joint)
Repairs/costs cited: Dealership that performed engine recall replacement unable to identify cause; problems intermittent making diagnosis difficult
Recalls/TSBs owners mention: No resolution provided despite return to dealership
Erratic engine shutter on acceleration and 4WD engagement
Engine shutter or vibration occurs intermittently at 40 MPH and escalates to violent shaking when 4WD engaged on inclines. Symptoms feel like driving over potholes or rumble strips. Dealer unable to duplicate or identify problem.
When: Intermittent; during normal driving at 40 MPH; when 4WD engaged going uphill
Symptoms owners cite: Dull shutter at 40 MPH as though going over potholes; Intermittent rumble-strip-like sensation; Violent shaking when 4WD engaged on incline; Transmission appears to drop during shaking; Occurs regardless of time, day, weather, or drive period
Repairs/costs cited: No repairs performed; dealers unable to duplicate issue; one technician no-show for scheduled ride-along
Recalls/TSBs owners mention: Dealer unable to identify problem after two visits and multiple days of inspection
Seatbelt inoperability and lane-keep assist failure
Child's seatbelt does not function and lane-keep assist feature not working on 2021 Sierra at 36,500 miles.
When: At 36,500 miles
Symptoms owners cite: Seatbelt does not work; Lane-keep assist does not work
Repairs/costs cited: No repair information provided
Recalls/TSBs owners mention: No response noted
Hard starting / delayed crank
Truck requires prolonged cranking (20 seconds) or multiple attempts to start after sitting parked for 15–20 minutes. Problem recurs repeatedly.
When: After parking for 15–20 minutes; random episodes
Symptoms owners cite: Truck keeps cranking with no start for ~20 seconds; Requires second attempt to fire up; Occurs after short parking periods (grocery store, etc.)
Repairs/costs cited: No repair information provided; problem dismissed as manufacturing defect causing parasitic draw
Recalls/TSBs owners mention: Dealership claims this is normal; refuses to address
Electrical defect causing sudden stalling while driving
Vehicle stops suddenly while driving with no warning lights, leaving owner stranded. Problem occurs multiple times and requires towing. Dealer attributes to manufacturing defect but offers no repair.
When: Multiple incidents since January 2025; third occurrence at 18,000 miles
Symptoms owners cite: Truck stops suddenly while driving; No warning lights before stalling; Vehicle required towing after stalling; Recurring problem with same symptoms
Repairs/costs cited: Replaced battery but did not resolve issue; no other repairs completed despite multiple shop visits
Recalls/TSBs owners mention: Dealer attributes to manufacturing defect but provides no repair or solution; delayed communication with owner
Synthesized from 50 NHTSA owner complaints — unverified consumer allegations, summarized for patterns. The verbatim filings appear below.
What owners are reporting 3 most recent
my truck keeps having this same issue since [XXX], always take it to team Gillman second august 26 same reason they replaced the battery but is a manufacturing defect while i am driving stops out of sudden AND THIS IS THE THIRD TIME THEY SUPPOSED TO CALL ME I HAVENT RECEIVE NO CALL IS AT TEAM GILLMAN SAME REASON ONLY HAS 18000 MILES MY NAME IS [XXX] CELL [XXX] INFORMATION REDACTED PURSUANT…
The contact owns a 2021 GMC Sierra 1500. The contact stated while driving at various speeds, the tailgate opened unintendedly. No warning light was illuminated. The vehicle was taken to the dealer but was not diagnosed or repaired. The dealer informed the contact that the VIN was not included in GM Campaign Number: N232426401. The manufacturer was not notified of the failure. The failure mileage…
Had electrical trouble with your 2021 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 2021 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?
Based on the 50 complaints filed, electrical issues most often appear around 32,897 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/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.