P0451 Code: Meaning, Causes, Symptoms (& How to Fix)

The evaporative emission control (EVAP) system is the most vital of modern vehicles. It collects the raw fuel that leaves the fuel system or fuel tank. This system contains an EVAP pressure sensor. The EVAP pressure sensor is most commonly installed on top of or inside the fuel tank. When the powertrain control module (PCM) of your vehicle monitors an issue with the EVAP pressure sensor signal, it triggers the P0451 code. This article mainly explains the P0451 code causes, symptoms and fixing cost.

P0451 Code Definition

The diagnostic trouble code (DTC) P0451 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.

P0451 code

Fuel is an evaporative fluid. As fuel sits in a car’s gas tank, some amount of this fuel starts evaporating over time.

The EVAP system of your vehicle uses to collect the raw fuel that exits the fuel tank and fuel system. The EVAP system transfers the collected fuel vapors back into the engine intake, from where they are transferred into the engine combustion chamber.

The evaporative pressure switch/sensor monitors and regulates the vacuum or air pressure in the evaporative emission (EVAP) system. This sensor is installed inside or on top of the fuel tank.

Your car PCM triggers the P0451 code when it detects the evaporative pressure sensor (also known as a fuel tank 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.
  • Fuel odor coming from the engine compartment (very rare). This fuel odor most commonly comes due to a damaged or faulty evaporative emission control pressure switch. A bad evaporative emission control pressure switch can’t stop the fuel vapors from leaking into the environment.
  • Poor fuel economy (rare)

Causes of P0451 Code

The following are the most common causes of the P0451 code.

  • Damaged fuel storage tank
  • Damaged wiring or loose connections of the 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 fuel pump
  • Faulty evaporative emission control 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 evaporative emission control system 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?

  • Replacing or repairing the faulty or leaking gas tank
  • Replacing the bad canister vent valve
  • Replacing the bad evaporative emission control system pressure sensor
  • Repairing the vacuum hose
  • Cleaning the bad purge vent 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 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: 

PartsCost
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 uses 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)

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