The evaporative emission control (EVAP) system is the most vital of modern vehicles. It collects the raw fuel vapors that leave the fuel tank and transfers them back to the combustion chamber. This system contains an EVAP system pressure sensor. The P0451 engine code indicates an issue with the EVAP pressure sensor of your vehicle.
The EVAP system pressure sensor (also known as a fuel tank pressure sensor) is most commonly installed on top or inside the fuel tank. When the powertrain control module (PCM) of your vehicle monitors an issue with the EVAP system pressure sensor signal, it triggers the P0451 code. This article mainly explains the P0451 code causes, symptoms, and how to fix it.
P0451 Code Definition
The P0451 code stands for “Evaporative Emission System Pressure Sensor/Switch.”
What does the P0451 Code Mean?
The P0451 code indicates that your powertrain control module (PCM) detects an improper or incorrect voltage signal from the evaporative emission control system pressure sensor.
Fuel is an evaporative fluid. As fuel sits in your vehicle’s fuel tank, some amount of this fuel starts evaporating over time.
The modern vehicle models contain an EVAP system to collect the raw fuel vapors that exit the fuel tank and fuel system. The EVAP system then transfers the collected fuel vapors back into the engine intake, from where they are transferred into the engine combustion chamber.
The EVAP system pressure sensor monitors and regulates the vacuum or air pressure in the EVAP system. This sensor is installed inside or on top of the fuel tank.
Your car PCM triggers the P0451 code when it detects that the EVAP system pressure sensor pressure change values are not within the manufacturer-specified range.
Similar to code P0451 code, the P0450, P0452, P0453, P0454, P0455, P0456, P0457, P0458, and P0459 codes are also evaporative emission trouble codes.
Symptoms of P0451 Code
Usually, when your vehicle triggers the P0451 code, your vehicle doesn’t show adverse or noticeable symptoms. In most cases, the only symptom of the P0451 is the check engine light flashing.
Following are some other symptoms of the P0451 code:
- Check engine light is on
- Fuel odor coming from the engine compartment (very rare). This fuel odor most commonly comes due to a damaged or faulty EVAP system pressure switch. A bad EVAP pressure switch can’t stop the fuel vapors from leaking into the environment.
- Poor fuel economy (rare)
- Hissing noise while the engine is operating
- A bad EVAP system pressure sensor may also lead to emissions test failure. In some cases, your vehicle won’t be able to pass the emissions test with the P0451 code.
Causes of P0451 Code
The following are the most common causes of the P0451 code.
- Damaged fuel tank
- Vacuum leaks
- Damaged wiring or connectors connected to the EVAP system
- Bad or loose fuel cap
- An issue with the charcoal canister (rare)
- Faulty purge control valve
- Faulty fuel tank pressure switch
- Shorted or open circuit of the fuel tank pressure sensor
- A leak in the EVAP system
- Bad fuel pump
- Faulty EVAP system pressure sensor
- Bad PCM (rare)
How to diagnose the P0451 Code?
You need the following tools to fix or diagnose the P0451 code:
- OBD-II scan tool
- Flathead screwdriver
- Basic hand tools
Follow the below-given steps to diagnose the P0451 code:
- Verify the trouble codes saved in the memory of PCM using an OBD-II scanner.
- Use the freeze data to ensure the existence of the P0451 code.
- Clear the codes and perform a test drive of your vehicle. If the code returns, move forward for further inspection.
- Perform a visual inspection of the EVAP pressure sensor wires for corrosion or damage.
- Inspect loose electrical connections of the evaporative emission control system pressure sensor.
- Inspect the purge control valve for damage.
- Inspect the vapor hoses for a leak or damage.
- Inspect the vacuum system and all other parts of the EVAP system for damage or leak.
- Properly inspect the powertrain control module (PCM) of your vehicle. Update the PCM software if needed.
- After each inspection and repair, clear the codes and retest the engine until the problem is fixed.
Common Diagnostic of P0451 Code
- No proper inspection of all the electrical connectors, wiring, and parts before replacing any part of the EVAP system.
- Replacing the evaporative emission control system pressure sensor or vacuum hose without inspecting the connectors and wiring.
- Note clearing the PCM memory after fixing the issue.
Note: When troubleshooting P0451 Nissan and Cadillac P0451, start with the wiring connectors and gas cap before replacing any EVAP system components.
What repairs can fix the P0451 Code?
One or more of the following repairs can fix the P0451 code:
- Replacing the damaged gas tank
- Replacing the issues related to the charcoal canister
- Replacing the bad EVAP pressure sensor
- Repairing the vacuum hose
- Replacing the bad purge valve
- Cleaning the clogged purge valve
- Replacing or repairing the damaged wiring of the EVAP system
- Fixing the loose electrical connections
- Fixing a leak in the fuel storage tank
- Replacing the damaged gas cap
- Replacing or reprograming the PCM (rare)
P0451 Code Repair Cost
The repair or fixing cost of the P0451 code depends on your vehicle model, labor cost, and the nature of the repair. To fix the P0451 code, you need one or more of the below-given repairs:
| Parts | Cost |
|---|---|
| EVAP Pressure Sensor replacement | $280 to $352 |
| PCM replacement | $240 to $3000 |
| Purge valve replacement | $140 to $320 |
| Fuel gauge sender replacement | $240 to $410 |
FAQ Section
What is an EVAP pressure sensor?
The EVAP pressure sensor is a unit that is installed to measure the air pressure or vacuum in the evaporative emission (EVAP) system. It is also known as a fuel tank pressure sensor. The EVAP pressure sensor is most commonly installed on top of the fuel tank.
How serious is the P0451 Code?
The P0451 code is not a serious trouble code. But the existence of this code indicates that there is something wrong with the EVAP system of your car. You need to fix this code as soon as possible.
Where is the EVAP pressure sensor located?
The EVAP pressure sensor or fuel tank pressure sensor is one of the major parts of the fuel pump assembly and is installed on top of the fuel tank or inside the fuel tank. It is a part of the evaporative emissions (EVAP) system. It reads pressure in the fuel system to sense evaporative leaks, such as a bad or loose fuel cap.
Can I drive with a P0451 Code?
Yes, you can drive with the P0451 code for a short period of time, but you should only drive for a short time with this code. This code usually doesn’t produce drivability issues, but it may sometimes appear with other more serious trouble codes.
What are the causes of P0451 Mazda?
- Damaged fuel storage tank
- Bad fuel pump
- Damaged wiring or loose connections of the evaporative emission control system pressure sensor
- Faulty evaporative emission control system pressure sensor
- Bad or loose fuel cap
- Bad canister vent valve (rare)
- Faulty fuel tank pressure switch
- Shorted or open circuit of the fuel tank pressure sensor
- An issue with the fuel tank sending unit
- Bad PCM (rare)
Read More
- P0452 Code Meaning and Causes
- P0496 Code Meaning and Causes
- P0456 Code Meaning and Causes
- P0430 Code Meaning and Causes