This bulletin provides updated parts information and a service procedure to follow for removing accumulated carbon deposits from fuel injectors and internal engine components (e.g. intake valves and / or manifold, and combustion chambers). (This is an revised version of the original bulletin.)
full bulletin at NHTSA ↗2020 Subaru Ascent engine problems
severe Owners of the 2020 Subaru Ascent have filed 10 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
10
Recalls
0
Avg fix
$3,100
| Model year | engine complaints |
|---|---|
| 2019 Ascent | 21 |
| 2020 Ascent (this page) | 10 |
| 2021 Ascent | 5 |
| 2022 Ascent | 5 |
1crash
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.
This bulletin provides updated parts information and a service procedure to follow for removing accumulated carbon deposits from fuel injectors and internal engine components (e.g. intake valves and / or manifold, and combustion chambers). (This is an revised version of the original bulletin.)
full bulletin at NHTSA ↗This bulletin outlines the diagnostic and repair procedure for white smoke emitted from the exhaust after startup.
full bulletin at NHTSA ↗This bulletin announces the design change made to the exhaust manifold flange nut material that has been changed from stainless steel to medium carbon steel. This change also necessitates a revised tightening torque specification. (This is an revised version of the original bulletin.)
full bulletin at NHTSA ↗This bulletin provides updated parts information and a service procedure to follow for removing accumulated carbon deposits from fuel injectors and internal engine components (e.g. intake valves and / or manifold, and combustion chambers).
full bulletin at NHTSA ↗Source: NHTSA manufacturer communications. Bring the bulletin number to your dealer or shop.
The failure pattern owners describe
Owners report a range of engine and related powertrain failures across 2020 Subaru Ascents. The most dramatic complaint involves sudden uncontrolled acceleration at low speed with brake failure and disabled safety systems—the vehicle accelerated violently onto a driveway without foot input, crashed through a garage, and required ignition shutoff to stop. Another owner experienced a PCV valve failure at highway speed (70 mph) causing catastrophic engine damage with no prior warning; the part was recalled on 2019 models. Electrical charging system failures appear in two reports: one owner's alternator failed at 26,000 miles after battery replacement, causing total power loss on busy streets; another's serpentine belt shredded at 1,289 miles, triggering battery and overheating warnings. An engine overhaul was required at 120,000 miles due to cam carrier leaks and oil-burning odor. One owner reports engine sludge accumulation requiring replacement at 82,000 miles, citing forums indicating this may be manufacturer-related. Check engine lights and disabled safety features appear in multiple reports, sometimes tied to undiagnosed issues or previous-owner recalls. A fuel system concern involves persistent gasoline smell during idle across multiple 2019–2021 models, with owners questioning safety parallels to historical issues. Transmission jerking under acceleration was reported alongside a spontaneous windshield crack. No owners report warning signs prior to most failures.
Same Subaru Ascent engine reports on nearby years: 2019
Failure modes owners describe
Uncontrolled acceleration with brake and safety system failure
Vehicle accelerated violently without operator input while parked on driveway; brakes had no effect and automatic emergency braking/forward collision warning failed to activate.
When: Low speed, driveway entry, no prior warning
Symptoms owners cite: Sudden full-throttle acceleration without pedal input; Brakes unresponsive; Automatic braking system inoperative; Forward collision warning malfunctioning; Engine continued receiving fuel regardless of accelerator position
Repairs/costs cited: Vehicle required ignition shutoff to stop; totaled in crash
PCV valve failure causing catastrophic engine damage
PCV valve failure caused loss of engine function on interstate highway at speed, resulting in catastrophic engine damage requiring teardown inspection.
When: 70 mph highway speed, approximately 42,000 miles for similar symptom complaint
Symptoms owners cite: Engine failure at highway speed; No prior warning signs; No warning lights before failure
Repairs/costs cited: Engine teardown performed; part recalled in 2019 models
Recalls/TSBs owners mention: Part recalled in 2019 models for possible loss of control from engine failure
Alternator failure with total power loss
Alternator failed at 26,000 miles after battery replacement two weeks prior, causing complete electrical system loss on busy streets.
When: At 26,000 miles; failure occurred two weeks after battery replacement
Symptoms owners cite: Battery died after two weeks of replacement; Eyesight disabled light illuminated first; Dashboard lights flashed on (Christmas Tree effect); Loss of power steering; Total power loss on roadway; Hazard lights inoperative
Codes mentioned: Battery light illuminated after failure
Repairs/costs cited: Subaru replaced battery initially; later diagnosed alternator failure; parts retained by Subaru for warranty replacement
Recalls/TSBs owners mention: Warranty replacement performed; parts held by manufacturer
Serpentine belt shredding
Serpentine belt shredded at extremely low mileage, causing loss of cooling circulation and triggering battery and overheating warnings.
When: At 1,289 miles, within first few days of ownership
Symptoms owners cite: Battery light illuminated; Vehicle started to overheat; Check coolant indicator illuminated; Smoke from engine bay; Serpentine belt shredded; Coolant sprayed throughout engine compartment
Codes mentioned: Battery light, Overheating indicator
Repairs/costs cited: Serpentine belt replaced at dealership
Cam carrier leak with engine wear
Cam carrier leak detected, followed by oil-burning odor and diagnosis of required engine overhaul at 120,000 miles.
When: Approximately 120,000 miles
Symptoms owners cite: Abnormal odor of oil from vehicle; Oil-burning odor while driving; Cam carrier leaking from engine
Repairs/costs cited: Engine overhaul required; no recall coverage; manufacturer provided no assistance
Recalls/TSBs owners mention: No recall coverage available; manufacturer declined to provide assistance
Engine sludge requiring replacement
Engine sludge accumulation requiring complete engine replacement at 82,000 miles on a maintained vehicle; owner reports forums indicate this is common across this make/model.
When: At 82,000 miles
Symptoms owners cite: Engine sludge accumulation
Repairs/costs cited: Engine replacement required
Persistent fuel odor during idle
Faint gasoline smell during idle or stopped conditions, reported by owner as occurring every time vehicle stops; owner found forum posts indicating 2019–2021 models have same issue from 2,100 to 90,000 miles.
When: Occurs consistently during idle and stop; low mileage to 90,000 miles across affected models
Symptoms owners cite: Faint gasoline smell at idle; Odor occurs every time vehicle is stopped
Repairs/costs cited: Dealership referenced old service recall for low pressure fuel pump; no diagnosis confirmed; multiple trips and diagnostic charges reported by other owners
Recalls/TSBs owners mention: Old service recall exists for low pressure fuel pump; dealership advised not to rely on online reports
Check engine light with disabled safety features
Check engine light and disabled safety systems appeared during freeway driving; owner later discovered a recall was on file for previous owner only, not transferred to new buyer.
When: During freeway driving; mileage not specified
Symptoms owners cite: Check engine light illuminated; All safety features disabled; No warning given at time of purchase
Codes mentioned: Check engine light
Repairs/costs cited: Recall identified; case manager indicated recall was for previous owner only and declined support
Recalls/TSBs owners mention: Recall on file; manufacturer case manager stated recall was for previous owner and cannot assist current owner
Transmission jerking with elevated RPM
Transmission stalls or jerks when engaging gear or changing gears with elevated RPMs that do not result in vehicle response.
When: Mileage not specified
Symptoms owners cite: Transmission stalls when going into gear; Transmission jerks when changing gears; RPM elevated but vehicle fails to respond; No warning signs; Spontaneous windshield crack (separate issue in same report)
Repairs/costs cited: No diagnosis reported; Subaru stated no recall exists
Recalls/TSBs owners mention: Subaru stated no recall; referred to customer service
Accelerator pedal jerking with no vehicle response
Vehicle jerked when accelerator pedal depressed at low speed; RPMs elevated but vehicle failed to accelerate or respond.
When: At 42,000 miles during 10 mph drive
Symptoms owners cite: Vehicle jerked when accelerator depressed; RPMs elevated; Vehicle failed to respond to throttle input; No warning light illuminated
Repairs/costs cited: Vehicle not diagnosed or repaired
Recalls/TSBs owners mention: Manufacturer confirmed VIN not included in any recall
Synthesized from 10 NHTSA owner complaints — unverified consumer allegations, summarized for patterns. The verbatim filings appear below.
What owners are reporting 0 most recent
Had engine trouble with your 2020 Subaru Ascent?
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 2020 Subaru Ascent?
It's a meaningful issue. 10 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 10 complaints filed, engine issues most often appear around 54,430 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/2020/Subaru/Ascent.
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.