P0451 EVAP Pressure Sensor Reading Out of Range
Drive normally - check soon
The sensor that measures pressure in the fuel tank gives readings the computer does not believe. The sensor, its wiring or a vapor system problem is the cause. Harmless to drive, but it fails emissions tests.
- Safe to drive?
- Yes
- Typical cost at a shop
- $61-$423 RepairPal national averages, parts and labor
- Emissions test
- Yes, while the check engine light is on, most OBD emissions tests fail the car.
Watch the fuel tank pressure live and see if the EVAP pressure sensor reading makes sense.
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What it means
The fuel tank pressure sensor tells the computer whether the vapor system holds its seal during the EVAP leak test. P0451 means its reading is out of the expected range, does not change when it should, or jumps around.
The technical version
The computer checks the tank pressure sensor for plausibility: near zero with the cap off or the vent open, and changing when purge pulls a vacuum. P0451 sets when the reading fails those checks. P0452 and P0453 are the low and high circuit codes. On some cars a blocked vent or a full canister gives readings that look like a bad sensor.
Official name: Evaporative Emission Control System Pressure Sensor Range/Performance.
Symptoms
- Usually only the check engine light.
- Sometimes other EVAP codes.
Causes, most likely first
| Cause | How likely | How to tell |
|---|---|---|
| A faulty fuel tank pressure sensor | most common | With the cap off, it does not read near zero. |
| Wiring or connector problems at the sensor | common | The reading jumps when you move the harness. |
| A blocked vent line or vent valve | less common | The tank holds pressure or vacuum; P0446 may appear. |
| A pinched or blocked sensor hose (on cars with a remote sensor) | rare | Visible damage to the small hose. |
How likely is our ranking from repair data and common practice, not a published rate.
What the live data shows
Many cars show fuel tank pressure. With the engine off and the gas cap removed, it should read about zero. It should move when the engine runs and purge opens, then settle. A reading stuck at one value, or one that jumps around, points to the sensor or its wiring.
What to check first, in order
-
Read tank pressure with the cap off.
A good sensor reads about zero.
What the data shows: Close to zero.
Cost: no cost if you have a scanner
-
Inspect the sensor connector and wiring at the tank.
Corrosion is common under the car.
What the data shows: No reading needed.
Cost: free to look
-
Check the vent line and vent valve.
A blocked vent can look like a bad sensor.
What the data shows: Not a scanner step.
Cost: $61-$90 at a shop (Emission system diagnosis (shop), RepairPal)
-
Replace the tank pressure sensor.
The usual fix.
What the data shows: Readings look normal and EVAP readiness completes.
Cost: $333-$423 at a shop (Fuel tank pressure sensor replacement, RepairPal)
Is it safe to drive?
Drive normally - check soon
Yes. It is a fuel vapor fault, not a fuel leak.
Harmless to drive with. The computer cannot run its leak test with a bad pressure reading, so you will fail an emissions test until it is fixed.
Stop driving and get help if
- You see liquid fuel dripping or smell strong fuel inside the car.
What it costs
| Repair | Typical cost |
|---|---|
| Emission system diagnosis (shop)RepairPal, updated September 3, 2026 | $61-$90 |
| Fuel tank pressure sensor replacementRepairPal, updated June 18, 2026 | $333-$423 |
National averages for the full job at a shop, parts and labor, from RepairPal (updated June 18 and September 3, 2026). Your price depends on the car and the area. Many of the first checks on this page cost nothing with a scanner.
Can I clear it? Will it come back?
The EVAP test only runs under certain conditions, often a cold start after the car has sat for hours, with the tank between about a quarter and three quarters full. After the repair, clear the code and drive normally for several days. The EVAP monitor should show complete and the code should stay away.
Will it fail an emissions test?
Yes, while the check engine light is on, most OBD emissions tests fail the car.
Related codes
How Obie handles P0451
Obie reads fuel tank pressure and the EVAP codes and tells you whether the sensor reading looks believable. Obie is part of ScanMyCar Pro. Codes and live sensors are free.
Questions people ask
Where is the fuel tank pressure sensor?
On most cars it is on top of the fuel tank or near the canister. Some jobs need the tank lowered.
Can I drive with P0451?
Yes. It does not affect how the car runs, but it fails emissions tests.
Can a gas cap cause P0451?
Rarely. Check the cap anyway, but the sensor and its wiring are the usual suspects.
Sources
- RepairPal: P0451 code page repairpal.com
- RepairPal: Emission system diagnosis (shop) (updated September 3, 2026) repairpal.com
- RepairPal: Fuel tank pressure sensor replacement (updated June 18, 2026) repairpal.com
- Texas DPS emissions testing FAQ dps.texas.gov
- Arizona myazcar.com: OBD and the check engine light myazcar.com
A guide, not a diagnosis. This page describes what P0451 generally means across OBD2 cars. What is actually wrong with your car depends on its live data and its history, and any repair decision deserves a proper diagnosis, whether that is you with a scanner or a professional with a lift.