P0451: The EVAP fuel tank pressure sensor is reading out of range
Evaporative Emission Control System Pressure Sensor Range/Performance
The fuel tank pressure sensor reading does not make sense to the computer. Get it checked within a couple of weeks. If you smell strong gas, get it checked right away.
Stop driving and get help if
- The check engine light is flashing
- The temperature gauge runs high, or you see steam (overheating)
- The car loses power, hesitates badly or stalls
- You smell burning or see smoke
- A brake warning light comes on, or the brakes feel different
Pull over as soon as you can, turn the engine off, and call a tow or roadside help.
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 the fix could involve
From the cheaper fix to the bigger one. Prices depend on your car, your area and the shop, so ask for a written quote that names the part and the labor before you approve it.
- Fuel tank pressure sensor replacement
- Wiring or connector repair
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 reads P0451 alongside any related EVAP codes and shows your live fuel level, which matters because many EVAP tests only run within a certain fuel range. Get Lewis on the App Store or Google Play.
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.
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