What happens if I keep overfilling my gas tank?

Repeatedly overfilling forces liquid fuel into the charcoal canister, which is designed for vapor only. This damages the canister and can cause multiple EVAP codes.

Can P0451 cause a false leak code like P0456?

Yes. If the pressure sensor reads incorrectly, the computer may see a pressure drop it interprets as a small leak, even when the system is sealed.

Is this sensor easy to replace?

On most vehicles it is accessible on or near the fuel tank. Difficulty varies by vehicle; some require dropping the fuel tank.

Codes › P0451

P0451: The EVAP fuel tank pressure sensor is reading out of range

Evaporative Emission Control System Pressure Sensor Range/Performance

Low severityCan you keep driving?

Yes. This is an emissions system issue and will not affect how the car drives. You will fail an emissions test while this code is active.

What it means

The EVAP fuel tank pressure sensor measures the pressure inside the sealed fuel system during self-tests. The computer uses these readings to detect leaks. P0451 means the sensor's output is outside the expected range or is not changing the way it should during the test. The sensor may be reading too high, too low, or not responding at all. The non-obvious trap here is that this sensor is directly exposed to fuel vapors, which can poison it over time. A faulty sensor can cause the computer to report leaks that do not exist, or miss real ones.

Common causes

Failing fuel tank pressure sensorProlonged exposure to fuel vapors degrades the sensor. Common on higher-mileage vehicles.
Clogged or blocked sensor portDebris or fuel contamination can block the port the sensor monitors.
Wiring or connector faultCorroded connector or damaged wires between the sensor and PCM.
Overfilled fuel tankTopping off past the first click can flood the charcoal canister and upset pressure sensor readings.

What it costs

Fuel tank pressure sensor replacement$80 to $250
Wiring or connector repair$60 to $200

Symptoms

Check engine light on
No change in driving
Possible additional EVAP codes stored alongside P0451
Failed emissions test

What to do next

Check whether you have a habit of topping off the fuel tank past the first click. Doing so can flood the EVAP canister and affect sensor readings. If that is not the issue, test the sensor voltage at idle; a healthy sensor should read around 1.0 to 1.5 volts with a sealed system. Have a shop verify with live data before replacing parts.

Lewis displays the live fuel tank pressure sensor voltage so you can see exactly what the computer is reading and compare it to the expected range. Download Lewis.

Related codes

FAQ

What happens if I keep overfilling my gas tank?: Repeatedly overfilling forces liquid fuel into the charcoal canister, which is designed for vapor only. This damages the canister and can cause multiple EVAP codes.
Can P0451 cause a false leak code like P0456?: Yes. If the pressure sensor reads incorrectly, the computer may see a pressure drop it interprets as a small leak, even when the system is sealed.
Is this sensor easy to replace?: On most vehicles it is accessible on or near the fuel tank. Difficulty varies by vehicle; some require dropping the fuel tank.