P0451 on Honda: How to Diagnose & Fix
Evaporative Emission System Pressure Sensor/Switch Range/Performance
1 Honda model · 1 documented issue · $25-$400 repair
P0451 on Honda by model: symptoms, diagnosis and fix
On the Honda Accord, P0442 (small EVAP leak) is one of the most common check-engine triggers and almost always traces to one of three components in order of likelihood: the fuel cap, the engine-bay canister purge valve, or the under-car canister vent solenoid. The gas cap's rubber O-ring hardens, cracks, and stops sealing with age (aftermarket caps are a frequent repeat offender on this model). When the cap is good, the electric canister purge valve (which sticks or leaks internally) and the vent solenoid are the next suspects. A common Honda giveaway is a P1457 or P0451/P0456 stored alongside P0442, which points to the canister vent-side hardware rather than the cap. Because the leak is small, it is often intermittent and may set after refueling.
Common Symptoms
- Check engine light on
- Occasional faint fuel odor
- No drivability change
- Code often returns after refueling
- Sometimes paired with 'check fuel cap' message
How to Fix
Start with the cheapest fix: inspect and replace the OEM fuel cap (Honda P/N varies by year and model, e.g. 17670-SDA-A01 on many 2005 sedans) with a genuine Honda cap, then clear the code and drive several drive cycles. If it returns, perform an EVAP smoke test to pinpoint the leak; the usual repair is replacing the canister purge valve (engine bay) or the vent solenoid (under the car near the charcoal canister). Avoid aftermarket gas caps, which commonly reseal poorly.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Honda 17670-SDA-A01 fuel-filler capOEMHonda 17670-SDA-A01
The catalog shows broad 2003-2004 coverage but narrower 2005 coverage; use VIN confirmation for 20
- Honda 17670-SHJ-A02 fuel-tank capOEMHonda 17670-SHJ-A02
Replace a confirmed failed cap on the later seventh-generation branch Fitment/availability: Selected 2005-2007 Accord configurations; supersedes 17670-SHJ-A01 and 17670-SHJ-A31.
- Honda 17670-T3W-A01 complete fuel-filler capOEMHonda 17670-T3W-A01
Replace a confirmed failed cap-seal branch on the eighth- or ninth-generation car Fitment/availability: 2008-2017 Accord L4 or V6 in the seller's listed US configurations.
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Sources for this issue (3)
P0451 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0451 mean on a Honda?
P0451 stands for "Evaporative Emission System Pressure Sensor/Switch Range/Performance." This code means the PCM detected that the EVAP system pressure sensor (fuel tank pressure sensor) is producing readings that are erratic, noisy, or outside the expected range. This sensor monitors pressure and vacuum in the fuel/EVAP system to detect leaks and manage vapor flow. A range/performance fault undermines the system's ability to run leak tests, which is an emissions issue. It usually triggers only the check engine light without affecting how the car drives. On Honda it is documented across 1 model: Accord.
What are the most common causes of P0451?
The most common causes of P0451 are: Faulty fuel tank/EVAP pressure sensor, Loose or faulty gas cap causing abnormal pressure, Damaged wiring or connector at the sensor, Blocked, kinked, or leaking EVAP hoses, Sensor contamination or internal fault, Failing PCM (less common). The specific cause varies by vehicle.
How much does it cost to fix P0451 on a Honda?
Published repair estimates on Honda range from $25 to $400 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
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Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.