P0451 Code: Meaning, Symptoms, Causes (& Repair Cost 2022)

The EVAP Pressure Sensor, also known as a Fuel Tank Pressure (FTP) Sensor, is a device that measures air pressure or vacuum in the evaporative emission (EVAP) system. Code P0451 is triggered when the FTP sensor signal falls outside the specified range for an extended period. This article mainly explains the P0451 code symptoms, causes, and fixing cost.

P0451 Code Definition

P0451 stands for Evaporative Emission System Pressure Sensor/Switch performance/range. This error code is set when the Powertrain Control Module (PCM) detects improper, erratic, or otherwise incorrect signal voltage from the EVAP sensor.

P0451 CODe

What does the P0451 Code Mean?

Fuel is an evaporative fluid. As gasoline sits in the car’s fuel tank, some amount of it will evaporate over time. As gasoline is escaping as vapor, the evaporative emission control pressure sensor will capture it and send it back to the engine’s combustion chamber for a re-burn.

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

Your car PCM triggers the P0451 when it detects that the evaporative pressure sensor (also known as a fuel tank pressure sensor) indicates pressure change values that are not within the manufacturer-specified range.

Symptoms of Code P0451

Most often, there are no adverse or noticeable symptoms of a P0451. In almost all cases, the only symptom will be the illumination of the Check Engine Light. In some other cases, you may notice fuel odor emitting from the engine bay.

The fuel odor is because a defective evaporative emission control pressure switch cannot prevent gasoline vapor from escaping into the atmosphere. In Ford vehicles, for instance, P0451 Ford Explorer and P0451 code F150 will appear along with other related EVAP diagnostics trouble codes.

Read More: Car Dashboard Warning Lights

Causes of P0451 Code

The P0451 code triggers for a variety of reasons. The following are the most common causes of the P0451 code.

  • A defect in, or damage to, the fuel storage tank
  • Loose or faulty gas cap
  • A lousy gas tank pressure switch.
  • A problem with the fuel tank sending unit
  • Damaged wiring
  • Faulty canister vent valve (rare)
  • Open or shorted fuel tank pressure sensor circuit
  • Faulty PCM (rare)

Read More: Causes of Faulty PCM

Common P0451 Code Diagnostic Mistakes

The most common mistake associated with a P0451 code is failing to properly inspect all components, wiring, and connectors before replacing any part of the evaporative emission control system. For example, in some cases, a vacuum leak could be due to a loose or damaged fuel cap, not a faulty vacuum hose.

In the same manner, when troubleshooting P0451 Nissan, Cadillac P0451 [or any vehicle you have], start with the wiring connectors and gas cap before replacing any EVAP system components. So, you understand it more; clearly, a loose gas cap could be the cause of vacuum leaks, not a faulty vacuum hose.

Tools Required to Diagnose P0451 Code

  • OBD-II scan tool
  • Flathead screwdriver

How to diagnose the P0451 code?

  1. Use an OBD-II scanner to identify the codes that the PCM has saved.
  2. Start addressing each code in the order in which it was stored. In most cases, when a P0451 code is stored, other related codes will be stored after it, so the P0451 code should be resolved first.
  3. The first thing to look for in this case, after identifying the code(s), will be damaged, corroded, chafed, or otherwise faulty wiring, connectors, and circuits. After repairing any instances of these, clear the code(s) and retest the system. 
  4. If your vehicle is still showing trouble code, then inspect the vapor hoses, the vacuum, the purge valve, charcoal canister and all other components related to the evaporative emission control system.
  5. After each inspection and repair, clear the codes and retest the engine until the problem is resolved.

What repairs can fix the P0451 Code?

In some instances, the repair for a P0451 code could be as simple as replacing the gas cap. Follow the below-given steps to fix the P0451 code:

  • Repair or replace the gas tank.
  • Replace the canister vent valve.
  • Repair or replace a faulty fuel tank pressure sensor.
  • Clean or replace the purge vent valves.
  • Replace damaged or defective wiring or connectors in the fuel tank pressure sensor circuit.
  • Replace or reprogram the PCM (rare).

Read More: How to repair the P2096 Code

Same Problems with Different Error Codes

A vehicle computer with a malfunctioning EVAP system can register a host of other trouble codes that mean the same or related problems with P0451. Here are trouble codes with the same or similar issues with P0451;

  • P0459
  • P0458
  • P0457
  • P0454
  • P0453
  • P0452
  • P0450
  • P0455
  • P0456

P0451 Repair Cost

The repair or fixing cost of the P0451 code depends on your vehicle model, labor cost, and the nature of the repair. Your vehicle’s fuel pressure sensor is an important tool that ensures you never use excess fuel and impact your car’s performance. The average replacement cost of the fuel gauge sender is from $240 to $410.

FAQ Section

What is an EVAP pressure switch?

The EVAP Pressure Sensor, also known as a Fuel Tank Pressure (FTP) Sensor, is a device that measures air pressure or vacuum in the evaporative emission (EVAP) system. This sensor is typically found on top of the fuel tank.

How Serious Is the P0451 Code?

The P0451 code issue is among the least severe OBD-II codes. However, the presence of this code shows there is an imminent problem in your car. The underlying problem requires an easy repair and not to leave it for long.

Can I drive with a P0451 Code?

A P0451 code usually has no impact on vehicle performance or driveability, but the code may sometimes appear alongside other more serious OBD-II codes.

Where is the EVAP pressure sensor located?

The fuel tank pressure sensor is part of the fuel pump assembly and is mounted on top of the tank or inside the tank. It’s part of the evaporative emissions system (commonly referred to as “EVAP”) and reads pressure in the fuel system to detect evaporative leaks, such as a loose or faulty gas cap.

Is the P0454 code serious?

When the P0454 Trouble Code appears, it indicates that there is an issue with the evaporative emission control system pressure sensor intermittent.

Is an EVAP leak the same as a vacuum leak?

An EVAP leak is the same thing as a vacuum leak. A vacuum leak will certainly cause the engine to run roughly. I would recommend having your vacuum levels checked with a vacuum gauge by a qualified professional to determine whether they are in specification.

What are the causes of EVAP leaks?

The most common causes for EVAP leaks include a defective leak detection pump bad, a failing purge valve, a damaged hose, or seals and O-rings.

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