P0451

EVAP System Pressure Sensor/Switch A Circuit Range/Performance

Q: Is it safe to drive with P0451?

Yes. This is an evaporative-emissions monitoring fault, not a mechanical hazard — the engine runs normally. It should still be fixed so the car can pass emissions.

Q: Can I just clear P0451?

It returns after the EVAP monitor runs again unless the sensor, wiring, or pressure source is corrected. Check the gas cap first — it's the easiest cause.

Evaporative emissions (EVAP) Generic OBD-II Low

What it means

P0451 means the evaporative-emissions pressure sensor is reporting values that are erratic or outside the expected range. That sensor measures pressure in the fuel-vapor system so the ECM can run leak checks. It's a monitoring fault rather than a driving problem — the car runs normally, but it can stop the EVAP monitor from completing and cause an emissions failure.

Low

Can I keep driving? Yes — this is an emissions-monitoring fault, not a driving hazard; the car runs normally and the main effect is failing emissions.

Real-world scan data

Seen in

106

scans in the past year

Found in

<0.1%

of scans

<0.1%

of scans that found faults

Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.

Common symptoms

What you'll notice

Check-engine light on
Failed emissions test or an incomplete EVAP readiness monitor
No noticeable change in how the car drives

Common causes

Most likely first

Faulty EVAP (fuel-tank) pressure sensor giving erratic or out-of-range readings — the most common causeLikely
Damaged or corroded wiring or connector at the sensorCommon
A loose gas cap or EVAP leak causing unexpected pressure the sensor reportsCommon
Purge or vent valve stuck, disturbing system pressureLess often
Rarely, a faulty ECMLess often

How to diagnose & fix

Work through it in order

Read freeze-frame data and check the fuel-tank pressure sensor reading for erratic or implausible values.
Make sure the gas cap is tight and inspect the sensor's connector and wiring for corrosion or damage.
Verify the purge and vent valves aren't stuck, which can skew what the sensor sees.
If the sensor reads out of range with good wiring, replace the EVAP pressure sensor, then clear and re-run the monitor.

FAQ

Quick answers

Is it safe to drive with P0451?+

Yes. This is an evaporative-emissions monitoring fault, not a mechanical hazard — the engine runs normally. It should still be fixed so the car can pass emissions.

Can I just clear P0451?+

It returns after the EVAP monitor runs again unless the sensor, wiring, or pressure source is corrected. Check the gas cap first — it's the easiest cause.

Read & clear P0451 yourself

Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.

▶ Get it on Google Play

✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX