The P0451 trouble code means the vehicle’s powertrain control module (PCM) has detected abnormal readings from the evaporative emission system (EVAP) pressure sensor. Specifically, the sensor’s signal is outside the manufacturer’s expected range during system operation or testing.
P0451 is defined as “Evaporative Emission Control System Pressure Sensor/Switch Range/Performance.” The code is set when the PCM detects pressure or vacuum readings from the EVAP pressure sensor that fall outside the specified range for too long.
The EVAP pressure sensor—also called the fuel tank pressure (FTP) sensor—measures pressure and vacuum inside the EVAP system. This data helps the PCM detect leaks and verify proper system operation during EVAP self-tests and normal driving.
The EVAP pressure sensor measures changes in pressure or vacuum within the EVAP system. It is typically located on top of or inside the fuel tank.
When the PCM commands an EVAP test, it expects pressure readings to change in a predictable way. If the readings don’t match expected values, the PCM may interpret this as a sensor performance issue and store code P0451.
In most cases, the only noticeable symptom of a P0451 code is:
There are usually no drivability problems, performance loss, or unusual sounds associated with this code.
Possible causes of a P0451 code include:
This code is generally considered straightforward, with a failing EVAP pressure sensor being the most typical cause.
P0451 is usually not an urgent or immediately dangerous code. However, it can prevent the EVAP system from running properly and may cause the vehicle to fail emissions or inspection testing.
Ignoring the code for long periods may also make it harder to detect real EVAP system leaks in the future.
If you’re not confident with electrical diagnosis or sensor testing, professional diagnosis is recommended.
Repairs depend on the confirmed cause of the problem:
Because there is no universal fix, accurate diagnosis is essential before replacing parts.
After completing repairs, clear the code using a scan tool. Drive the vehicle and allow the EVAP monitor to run to confirm the code does not return and the repair was successful.
P0451 stands for “Evaporative Emission Control System Pressure Sensor/Switch Range/Performance.”
Not directly. P0451 points to a sensor range or performance issue, not a confirmed leak.
Usually no. Most vehicles show no drivability symptoms beyond the check engine light.
The EVAP pressure sensor is typically mounted on top of or inside the fuel tank.
Yes. Damaged wiring or poor electrical connections can cause incorrect sensor readings.
Yes. It belongs to a group of related EVAP pressure sensor codes, including P0450 through P0459.
Yes. An active check engine light or incomplete EVAP monitor can result in a failed emissions inspection.
It’s possible but rare. PCM issues are usually considered only after sensor and wiring problems are ruled out.
If wiring checks and basic sensor testing do not reveal the cause, or if accessing the fuel tank is required, professional service is recommended. A qualified technician can safely diagnose EVAP system faults and confirm the correct repair.
Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.