Service Bulletin - Oil leak at timing chain tensioner inspection cover due to possible insufficient sealant adhesion on inspection cover.
full bulletin at NHTSA ↗2021 Honda Accord engine problems
severe Owners of the 2021 Honda Accord have filed 18 NHTSA complaints about the engine at roughly $3,100 to repair (U.S. federal records, as of July 2026). Source: NHTSA Office of Defects Investigation. See engine across all vehicles →
Complaints
18
Recalls
0
Avg fix
$3,100
| Model year | engine complaints |
|---|---|
| 2017 Accord | 34 |
| 2018 Accord | 350 |
| 2019 Accord | 86 |
| 2020 Accord | 41 |
| 2021 Accord (this page) | 18 |
| 2022 Accord | 18 |
1crash
When does it fail?
Of the 18 engine complaints filed for the 2021 Honda Accord, 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
Of the 18 model years of Honda Accord we track for engine problems, this one has the fewest owner complaints on file (18).
Is there a fix? Manufacturer service bulletins
The manufacturer has issued service bulletins covering engine on this vehicle — documented repair instructions, service campaigns, or warranty extensions sent to dealers. A TSB isn't a recall (it's not a free safety remedy), but it's the manufacturer acknowledging the issue and how to fix it.
Service Bulletin - During engine start in cold conditions, a miscalculation in the PCM causes the air-fuel ratio to exceed DTC rich criteria, resulting in the vehicle experiencing drivability concerns. This issue is most common in regions with cold weather.
full bulletin at NHTSA ↗Dealer Message - American Honda Motor Co., Inc. (AHM) is searching for certain 2018-2022 Accords with customer complaint of Charging System Problem (battery icon) or Auto Engine Idle Stop Problem Lamp coming on the Multi-Information Display (MID). To better understand the cause of this condition, AHM would like to collect specific parts from the vehicle prior to your attempting a repair of any kind.
full bulletin at NHTSA ↗Dealer Message - American Honda Motor Co., Inc. (AHM) is searching for certain 2018-2022 Accords with customer complaint of Charging System Problem (battery icon) or Auto Engine Idle Stop Problem Lamp coming on the Multi-Information Display (MID). To better understand the cause of this condition, AHM would like to collect specific parts from the vehicle prior to your attempting a repair of any kind.
full bulletin at NHTSA ↗Dealer Message - American Honda Motor Co., Inc. (AHM) is searching for certain 2018-2022 Accords with customer complaint of Charging System Problem (battery icon) or Auto Engine Idle Stop Problem Lamp coming on the Multi-Information Display (MID). To better understand the cause of this condition, AHM would like to collect specific parts from the vehicle prior to your attempting a repair of any kind.
full bulletin at NHTSA ↗Source: NHTSA manufacturer communications. Bring the bulletin number to your dealer or shop.
The failure pattern owners describe
Owners of 2021 Honda Accords, especially 1.5T and 2.0T turbocharged models, report head gasket failure as the dominant failure mode. The gasket leaks coolant rapidly—one owner refilled every two weeks—or fails completely, causing cylinder misfires, flashing check engine lights, and sudden power loss at highway speeds. The vehicle sometimes enters limp mode and stalls. One owner reported the engine would not exceed 2,000 RPM during failure events; another lost all power while driving on an interstate in heavy rain.
Failures begin early. One owner saw it at 30,000 miles, most report between 50,000 and 80,000 miles, and one at 100,000 miles. Owners have taken their vehicles to multiple dealerships; inspectors found fluids properly maintained and passed cylinder leakdown tests, yet power loss events continued. Dealerships have diagnosed a narrow or inadequate coolant passage in the cylinder head as the structural weak point.
Repairs run $5,998 to $8,000. One owner had the gasket and cylinder head replaced in October 2025 but experienced recurrent coolant loss by December 2025, still being diagnosed at a different dealership.
The 1.5T engine also exhibits timing chain stretch requiring replacement at 86,000 miles. One unrelated complaint describes sudden unintended acceleration while in Park, throwing occupants forward into a building.
Same Honda Accord engine reports on nearby years: 2018 · 2019 · 2020 · 2022
Failure modes owners describe
Head gasket failure
Coolant leaks from failed head gaskets, often between cylinder 2 and water jacket or across the entire gasket. Some owners report rapid coolant loss requiring refills every two weeks. Failures have occurred as early as 30k miles and as late as 100k miles, though most cluster in the 50-80k range. The 1.5T and 2.0T engines appear particularly susceptible. Owners and a dealership tech report this as a known design defect related to narrow or inadequate coolant passages in the cylinder head.
When: 30,000 to 100,000 miles; most reported between 50,000 and 80,000 miles. Narrative #3 indicates repair occurred October 2025, with recurrent failure by December 2025.
Symptoms owners cite: Flashing check engine light; Engine misfire (cylinder 2 most common); Rough idle and sputtering; Loss of engine power at highway speeds; Vehicle enters limp mode; Multiple warning lights (brake system, power steering, emissions, Honda Sensing, TPMS); Coolant loss visible as white smoke from engine; Inability to maintain speed or accelerate; Engine stalling
Codes mentioned: P0302 (cylinder 2 misfire), Check engine light
Repairs/costs cited: Dealership quoted repairs ranging $5,998 to $8,000 for head gasket and related work. Narrative #3 mentions head gasket and cylinder head were replaced at Honda dealership in October 2025. One owner replaced ignition coils and spark plugs as initial diagnosis before gasket was confirmed. Narrative #11 states $2,400 for timing chain replacement at 86k miles.
Recalls/TSBs owners mention: No recalls mentioned in narratives. Narrative #3 states Honda refuses to acknowledge manufacturing defect. Narrative #3 also references class action lawsuit in California.
Engine misfire with ignition system component failure
Initial symptoms resemble ignition coil or spark plug failure (cylinder-specific misfires), but replacement of these components fails to resolve the issue. Misfire recurs within weeks. Root cause diagnosed as head gasket, not ignition system. This misdiagnosis pattern appears multiple times in the narratives, suggesting owners may first address spark plugs and coils before discovering the underlying gasket failure.
When: Approximately 68k-74k miles for cases where diagnosis sequence is documented
Symptoms owners cite: Engine misfire in cylinder 2; Sputtering and rough running; Check engine light; Misfire recurs 3 weeks after coil and plug replacement
Codes mentioned: P0302 (cylinder 2 misfire)
Repairs/costs cited: Initial repair: ignition coil and spark plug replacement (owner states one coil and one plug cost was not specified). Repairs failed and owner had to pursue dealership diagnosis, leading to head gasket identification.
Unintended acceleration in Park
Vehicle accelerated on its own and propelled into a building even with transmission in Park position. No prior warning lights or symptoms. Incident occurred 11/20/2025. Vehicle has not been inspected since incident. This is a single, critical safety report that differs from the majority head gasket complaints but falls within the engine/powertrain system.
When: 11/20/2025; no mileage stated
Symptoms owners cite: Sudden unintended acceleration; Vehicle moved even with gear in Park; No prior warning signs; Vehicle hit building and threw occupants forward
Timing chain stretch (1.5T engines)
Timing chain stretches and requires replacement. One owner documented replacement at 86k miles. Narrative #11 notes this is very common in these motors. This represents a separate design weakness in the 1.5T turbo engine beyond head gasket issues.
When: 86,000 miles
Symptoms owners cite: Timing chain noise or performance degradation (not explicitly stated in narrative)
Repairs/costs cited: $2,400 for timing chain replacement at 86k miles
Synthesized from 18 NHTSA owner complaints — unverified consumer allegations, summarized for patterns. The verbatim filings appear below.
What owners are reporting 2 most recent
The contact's girlfriend owns a 2021 Honda Accord. The contact stated that while his girlfriend was driving at an undisclosed speed, the check engine warning light and several other unknown warning lights illuminated. Additionally, the contact stated that the engine was slightly misfiring while driving. An independent mechanic replaced the spark plugs and the ignition coils at the residence;…
Vehicle accelerated on its own and propelled the vehicle over a curb and into a building. This occured even though the gear shift was in the Park position. My grandchild and I were thrown forward as vehicle hit the building. Vehicle has not been inspected since incident occurred just yesterday, 11/20/2025. No warnings preceded the incident,
Had engine trouble with your 2021 Honda Accord?
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 engine problem on the 2021 Honda Accord?
It's a meaningful issue. 18 complaints have been filed and the failure mode causes operational problems for owners. Repairs average $3,100.
At what mileage does the engine typically fail?
Based on the 18 complaints filed, engine issues most often appear around 103,500 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 $3,100 for engine 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 engine?
No active recalls currently cover engine 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/Honda/Accord.
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.