Honda Clarity Problems: 4 Issues Every Owner Should Know
2017-2021 model years · Based on 630+ owner reports · Last updated March 2026
According to Au7o's analysis of 630+ owner reports, the 2017-2021 Honda Clarity has 4 documented known issues, with 1 rated critical by the Au7o research team. The most serious is Sudden Power Loss and Engine Over-Rev on Highway ($0-$150 repair). The most commonly reported issue is 12V Auxiliary Battery Drain When Vehicle Sits Idle with 210 owner reports. Across all issues, repair costs range from $0 to $1,200. Full technical analysis and DIY maintenance guides at au7o.io.
All 4 Known Issues
The Honda Clarity PHEV can experience a dangerous loss of power when transitioning from electric to gasoline engine operation, particularly under high-load conditions such as highway hills, cold weather, or when the battery is nearly depleted. The vehicle may drop from highway speed (60+ mph) to as low as 20 mph while the engine revs loudly but fails to deliver power, behaving as if the transmission is in neutral. The 1.5L Atkinson-cycle engine struggles to maintain speed when the electric motor assistance diminishes, and the power management software does not always transition smoothly between operating modes.
Common Symptoms
- Vehicle drops from highway speed to 20-30 mph unexpectedly
- Engine revs loudly but vehicle does not accelerate
- Power System Problem warning on dashboard
- Gear icon with exclamation mark appears
- Issue worsens in cold weather or on steep grades
How to Fix
Visit a Honda dealer for the latest PCM software update, which improves the hybrid-to-gas transition logic. Keep the battery charged above 2 bars when highway driving in cold weather. In HV mode on long highway grades, manually press the HV Charge button to maintain battery reserve for power blending. If power loss occurs, safely pull over, turn off the vehicle for 60 seconds, then restart — this resets the power management system. The issue is less severe after the 2019 software updates.
What Owners Are Using
Parts and tips from 180+ owners who fixed this issue
- TipOn highway trips longer than your EV range, use HV mode from the start rather than draining the battery completely. Keeping 20-30% battery charge allows the electric motor to supplement the gas engine on hills, preventing the power loss scenario entirely.
- TipIf you experience frequent power loss on your commute, ask the dealer specifically for TSB 19-056 and TSB 20-008 software updates. Not all dealers proactively apply these unless you request them.
The Honda Clarity PHEV may fail to start charging when plugged in, or may stop charging before the high-voltage lithium-ion battery reaches full capacity. The onboard charger or charging control software may not properly communicate with the EVSE (charging station), resulting in no charging activity despite the plug being connected and the charge indicator light not illuminating. Some owners also report the battery only charging to partial capacity (6-36 miles range instead of the expected 47 miles), which may indicate battery degradation or a software calibration error in the battery management system.
Common Symptoms
- Charge indicator light does not illuminate after plugging in
- Charging starts but stops after a few minutes
- EV range significantly lower than expected after full charge
- Ready to Charge notification never appears on the dash
- Charging timer shows unreasonably long charge times
How to Fix
Try unplugging and re-plugging the charge connector firmly — a loose connection is the most common cause. If charging still fails, reset the vehicle by turning off, locking with the key fob, waiting 5 minutes, then plugging in again. Visit a Honda dealer for the charging system software update (TSB addresses EVSE communication). For range degradation, the dealer can run a battery health check — if capacity is below 66%, the battery may be eligible for warranty replacement under the 10-year/150,000-mile hybrid battery warranty.
What Owners Are Using
Parts and tips from 145+ owners who fixed this issue
- TipBefore assuming the charger is broken, test with a different Level 2 EVSE if possible. The Clarity can be picky about some aftermarket chargers. The OEM Honda charge cord and ChargePoint stations have the highest compatibility.
The Honda Clarity PHEV and EV models experience 12V auxiliary battery drain when the vehicle is not driven for extended periods (7-14 days). Unlike conventional vehicles, the Clarity's 12V battery is relatively small and powers multiple always-on systems including the telematics module, keyless entry receiver, and battery management system monitoring. The 12V battery does not charge from the high-voltage battery when the vehicle is off, leading to a dead 12V battery that prevents the vehicle from powering on even if the main traction battery is fully charged.
Common Symptoms
- Vehicle will not power on after sitting for a week or more
- Dashboard completely dark when pressing the start button
- Key fob does not unlock doors remotely
- Clock and radio presets reset after jump-starting
- Charging will not initiate even when plugged in
How to Fix
If the vehicle will sit unused for more than a week, connect a 12V battery tender or maintainer ($25-$40). The 12V battery is located in the trunk area. If the 12V battery dies, use a jump starter or jumper cables on the 12V battery terminals under the hood to boot the vehicle, then let it run for 30 minutes to recharge. Replace the 12V battery with a high-quality AGM battery every 3-4 years proactively ($150-$250). Consider unplugging the OBD-II port if you have an aftermarket dongle connected, as these draw parasitic current.
What Owners Are Using
Parts and tips from 210+ owners who fixed this issue
- TipA NOCO Genius1 or Battery Tender Junior ($25-$35) connected to the 12V battery when the car sits for extended periods completely eliminates this issue. Run the cable through the trunk seal — it compresses enough to close without damage.
The Honda Clarity PHEV is prone to AC condenser failures caused by refrigerant leaks. The condenser, located in front of the radiator, develops leaks from road debris impact or internal corrosion, gradually releasing all refrigerant from the system. Because the Clarity uses an electric compressor that also provides heating via a heat pump in some modes, the failure affects both cooling and heating performance. The issue is more common on 2018-2019 models and is exacerbated by the electric vehicle's reliance on the HVAC system for battery thermal management.
Common Symptoms
- AC blows warm air instead of cold
- Heating performance reduced in winter
- Visible refrigerant dye stains on the condenser
- Climate system warning light on dashboard
- Unusual hissing noise from the front of the vehicle
How to Fix
Have the AC system pressure-tested at a Honda dealer or qualified AC shop. If the condenser is leaking, it must be replaced ($600-$1,200 including labor and refrigerant recharge). Aftermarket condensers are available for $150-$250 for the part alone. Consider adding a condenser stone guard ($30-$50) to prevent future road debris damage. The entire HVAC system should be evacuated and recharged with the correct amount of R-1234yf refrigerant after condenser replacement.
What Owners Are Using
Parts and tips from 95+ owners who fixed this issue
- TipIf your AC gradually loses cooling over weeks, it is almost certainly a slow condenser leak rather than a low-charge situation. Adding refrigerant without fixing the leak is wasting money. Get a UV dye test to pinpoint the leak location before authorizing any repairs.
Frequently Asked Questions
What are the most common Honda Clarity problems?
According to Au7o's analysis of 630+ owner reports, the 2017-2021 Honda Clarity has 4 documented issues. The most frequently reported are: Sudden Power Loss and Engine Over-Rev on Highway, Intermittent Charging Failure and Battery Not Fully Charging, AC Condenser Refrigerant Leak and Cooling System Failure. Of these, 1 is rated critical and should be addressed promptly.
Is the Honda Clarity reliable?
The 2017-2021 Honda Clarity has 4 known issues documented across 630+ owner reports. 1 issue is rated critical: Sudden Power Loss and Engine Over-Rev on Highway. Prospective buyers should inspect for these issues and factor potential repair costs into their purchase decision. Regular maintenance following the manufacturer's schedule helps prevent many common problems.
How much does it cost to fix common Honda Clarity problems?
Repair costs for known Honda Clarity issues range from $0 to $1,200, depending on the specific problem and whether you choose DIY or professional repair. The most critical issue, Sudden Power Loss and Engine Over-Rev on Highway, typically costs $0-$150 to repair. Au7o provides step-by-step DIY maintenance guides that can help reduce repair costs.
What year Honda Clarity is the most reliable?
Reliability varies across model years of the Honda Clarity. Based on owner reports, issues are most commonly reported in earlier model years. Au7o recommends checking the specific known issues for your target year before purchasing, and having a pre-purchase inspection performed by a qualified mechanic. Our known issues database covers the 2017-2021 Honda Clarity with 4 documented issues from 630+ owner reports.
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