P0451: Fuel tank pressure sensor reading out of its expected range
EVAP pressure sensor range/performance
Severity: Monitor
EVAP faults let fuel vapour escape but rarely change how the car drives, and the main risk is a failed emissions test, so it is safe to drive while you arrange a fix.
It gets more serious if:
- Inspect soon: You keep smelling raw fuel around the car, not just right after filling up
- Stop: You see liquid fuel dripping or pooling under the car, or near the filler, tank or canister
P0451 in short
P0451 means the reading from the fuel tank pressure sensor, which the EVAP leak test relies on, does not make sense to the computer. Causes include a faulty sensor, a blocked sensor port, or software that a dealer update fixes. It is safe to drive while you arrange a check.
The EVAP leak test works by watching pressure or vacuum in the fuel tank, and the fuel tank pressure sensor provides that reading. The computer also checks that the reading itself is believable, and sets P0451 when it is not.
This is a plausibility code, not a wiring break. Makers have traced it to a sensor whose air reference port was blocked by water (GM), to tank and check-valve faults with a software update (Hyundai) and to PCM software (Ford).
Because the leak test depends on this sensor, P0451 often appears with leak codes such as P0455 or P0456. Check for a bulletin before replacing parts.
Most likely causes
Cause 1: Fuel tank pressure sensor giving implausible readings
Common general cause- Why it ranks here
- The code is a rationality check on this sensor, so the sensor itself is the first suspect when no bulletin applies.
- What would change this
- Rises if the reading is far off with the tank open to the air. Falls if the reading behaves normally.
Cause 2: Sensor air reference port blocked by water or condensation
Supported by vehicle data- Why it ranks here
- GM found normal water build-up could block the sensor port on several 2009–2010 models and fitted a cover.
- What would change this
- Rises on covered GM vehicles, or if the code comes and goes with wet weather or washing.
Cause 3: Engine computer software (some vehicles)
Supported by vehicle data- Why it ranks here
- Ford fixes P0451 on the 2019–2020 Ranger with a PCM reprogram, and Hyundai's Sonata fix includes an ECU update.
- What would change this
- Rises if your vehicle is covered by a software bulletin and is not yet updated.
Cause 4: Check valve, fuel pump cover or fuel tank fault (some Sonatas)
Supported by vehicle data- Why it ranks here
- Hyundai's bulletin for the Sonata inspects these parts and replaces the check valve or tank as needed.
- What would change this
- Rises on a covered Sonata where the dealer inspection finds a fault.
What to test first
Start at step 1. Each result tells you what it means and where to go next.
Step 1: Check whether your vehicle is covered by a P0451 bulletin, using the VIN at a dealer or the NHTSA site.
IfA 2019–2020 Ford Ranger, not yet reprogrammed
It meansHave the PCM reprogrammed.
IfA 2020–2023 Hyundai Sonata covered by 24-01-020H
It meansThe dealer inspects the check valve, pump cover and tank and updates the ECU.
Points to: Check valve, fuel pump cover or fuel tank fault (some Sonatas)
IfA 2009–2010 GM model listed in SB-10-06-04-001
It meansCheck the sensor port and fit the cover.
Points to: Sensor air reference port blocked by water or condensation
IfNo bulletin applies
It meansCheck the sensor reading.
Step 2: Have a shop compare the fuel tank pressure reading on a scan tool with the cap off (tank open to the air) against the service manual value.
Warning:Fuel vapour is flammable. Work outdoors with the engine off and cool, and keep sparks, cigarettes and open flames away.
IfThe reading is wrong or jumps around with the tank open
It meansInspect the sensor and its port.
IfThe reading looks right but the code keeps coming back
It meansAsk a dealer whether a software update exists for your vehicle.
Step 3: Have the shop inspect the sensor, its air reference port and its connector.
Warning:The sensor is usually on or near the fuel tank. Shop job: fuel vapour is flammable.
IfWater, dirt or a blockage at the reference port
It meansClear or protect the port as the maker says.
Points to: Sensor air reference port blocked by water or condensation
IfPort and connector are fine
It meansReplace the sensor.
Points to: Fuel tank pressure sensor giving implausible readings
Symptoms
- Check engine light on, usually with no change in how the car drives
- Fails an emissions or smog test because of the light or an incomplete EVAP monitor
- Persistent raw fuel smell around the car Gets more serious: stop and have it checked.
- Liquid fuel dripping under the car Gets more serious: stop and have it checked.
How to fix
Step 1: Check for an open bulletin or software update for your VIN before buying a sensor.
Step 2: After a repair, drive normally for several days so the monitor can re-run. Clearing codes or disconnecting the battery resets readiness, so do it shortly before an inspection only if you then complete a drive cycle.
Parts and cost context
- Fuel tank pressure sensor:Replace it only after a bulletin check and a reading check. On some vehicles a cover or a software update is the fix.
Labor varies by vehicle and shop; get a quote before you approve a repair.
Compare used part prices on PartPriceGuideOn your vehicle
HyundaiYour car
2020–2023 · Sonata
Supported by vehicle dataHyundai bulletin 24-01-020H covers P0451 on the 2021–2023 Sonata (DN8) and 2020–2022 Sonata (DN8A): inspect the check valve, fuel pump cover and tank, update the ECU, and replace the valve or tank if needed. The bulletin is on NHTSA, but whether it is still current is not verified, so it is labelled vehicle data rather than confirmed.
24-01-020HStatus unverified
P0451 stored in the ECU, inspect check valve, fuel pump cover and fuel tank, update the ECU
2020–2023sonata · issued · NHTSA 11010974
Covers the 2021–2023 Sonata (DN8) and 2020–2022 Sonata (DN8A). Inspect the check valve, fuel pump cover and fuel tank, update the ECU, and replace the check valve or tank if the inspection calls for it. A later version (25-01-001H) adds that the update replaces P0451 with a revised code. Only the NHTSA flat-file summary was reviewed, not the bulletin itself.
We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.
ChevroletYour car
2009–2010 · Silverado 1500
Supported by vehicle dataGM bulletin SB-10-06-04-001 links P0451 and leak codes to water blocking the fuel tank pressure sensor port, fixed with a sensor cover. The Cobalt, Colorado, GMC Canyon and Sierra and Pontiac G5 are also listed. The bulletin is on NHTSA, but whether it is still current is not verified, so it is labelled vehicle data rather than confirmed.
Where it is:Fuel tank pressure sensor air reference port
SB-10-06-04-001Status unverified
Intermittent MIL with P0442, P0446, P0451–P0455, install fuel tank pressure sensor cover
2009–2010cobalt, colorado, silverado-1500 · issued · NHTSA 10034369
Water or condensation can block the air reference port of the fuel tank pressure sensor and set leak or sensor codes now and then. The fix is a cover over the sensor. GMC Canyon and Sierra and Pontiac G5 are also listed. Only the NHTSA flat-file summary was reviewed, not the bulletin itself.
We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.
FordYour car
2019–2020 · Ranger
Supported by vehicle dataFord TSB 21-2010 says P0451 and/or P0456 can come from PCM software settings and is fixed by reprogramming the PCM. The bulletin is on NHTSA, but whether it is still current is not verified, so it is labelled vehicle data rather than confirmed.
TSB 21-2010Status unverified
MIL with P0451 and/or P0456 from PCM software parameters
2019–2020ranger · issued · NHTSA 10186414
Reprogram the PCM with the latest software. Only the NHTSA flat-file summary was reviewed, not the bulletin itself.
We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.
Related codes
P0451 questions
Is P0451 a leak?
Not by itself. It means the tank pressure reading does not make sense, so the computer cannot trust its leak test. It often appears alongside leak codes for that reason.
Should I just replace the pressure sensor?
Check for a bulletin first. Ford and Hyundai fix some cases with a software update, and GM fixed some by covering the sensor so water could not block its port.
Is it safe to keep driving?
Usually yes, as long as there is no strong fuel smell and no fuel dripping. Most makers advise getting it fixed when it is convenient. A strong fuel smell means get it checked soon, and dripping fuel means stop and do not drive.
Will this code fail an emissions inspection?
In states that test OBD-II, a check engine light that stays on with the engine running fails the test. Clearing the code does not help straight away, because the EVAP monitor then reads not ready until the car completes a drive cycle.
Sources and review
- Frequently Asked Questions on On-Board Diagnostics (EPA 420-F-97-003)
- On-Board Diagnostic II (OBD II) Systems Fact Sheet
- EVAP: The Phantom Emissions Menace (Nissan TechNews, May 2018)
- OBD Test Reference (rev 8.6)
- What do you mean my car is not ready?
- Recall acknowledgement 17V-088: BMW i3 REx fuel tank vent line may chafe
- Part 573 Safety Recall Report 15V-621 (Mazda 8615J): liquid fuel can enter the EVAP canister
- Cal. Code Regs. Tit. 13, § 1968.2 — Malfunction and Diagnostic System Requirements (OBD II)
- GM SB-10-06-04-001: intermittent MIL with P0442, P0446, P0451–P0455, install fuel tank pressure sensor cover
- Ford TSB 21-2010: P0451 and/or P0456 on 2019–2020 Ranger, reprogram PCM
- Hyundai 24-01-020H: P0451 on Sonata, inspect check valve, fuel pump cover and tank, ECU update
- Last reviewed
- Written by
- Saurabh K.
- Editorial review
- Pending
- Technician review
- Technician review pending
This page explains what a code usually means; it is not a substitute for a professional inspection. How we source and review · Report an error