P0451: EVAP System Pressure Sensor Range/Performance

What is P0451?

The DTC P0451 is defined as “Evaporative Emission Control System Pressure Sensor Range/Performance.” The Powertrain Control Module (PCM) logs the code P0451 when the EVAP system pressure sensor values are not within its specified range over an extended period.

The EVAP system comprises many critical components that work together to prevent harmful gas vapors from escaping into the environment.

These components include the following:

• Charcoal canister
• EVAP pressure sensor (or fuel tank pressure sensor)
• Purge valve solenoid 
• Vent control valve solenoid 
• Metal tube
• Rubber hose

So, how does this complex system work?

Over time, the fuel sitting in the fuel system tends to evaporate.

The EVAP system uses the fuel vapor pressure to propel the evaporated fuel into the charcoal canister via a complex network of metal tubes and rubber hoses.

When the conditions are ideal, the purge valve solenoid draws these vapors into the engine, where they are burned.

The EVAP pressure sensor works with the EVAP system to capture the evaporated fuel, preventing it from leaving the system. This fuel pressure sensor (located in the fuel tank and joined to the fuel pump) also communicates with the PCM, alerting it if there’s a vacuum leak within the system.

The Powertrain Control Module regularly monitors the fuel tank pressure sensor signal. If the PCM detects that the signal voltage from the fuel tank pressure sensor is not within the specified range, it’ll turn the Check Engine Light on and log the trouble code P0451.

Common symptoms

Here are some obvious signs indicating a fuel pressure sensor malfunction: 

1. An Illuminated Check Engine Light

While the Check Engine Light on your dashboard could indicate an EVAP pressure sensor malfunction, it could also signify several other issues.

So, if you see the Check Engine Light illuminated on your dashboard, you can use an OBD2 scan tool to determine the engine codes stored in the Powertrain Control Module.

2. The Smell Of Gas Vapors From The Engine

Sometimes a faulty EVAP system may result in fuel vapor escaping from the charcoal canister, subsequently exuding a gasoline smell.

Typically, this problem occurs due to a broken or damaged EVAP canister and must be fixed soon. But it could happen due to a faulty EVAP sensor too. Failing to address the issue could result in your vehicle failing the emissions test.

3. A Drop In Fuel Economy

A decrease in fuel economy is a common sign of a faulty fuel tank pressure sensor (FTP sensor.)

While several other factors could also cause a drop in gas mileage, in this case, the problem occurs due to fuel vapor escaping the fuel tank.

Your vehicle ends up burning more fuel than usual, resulting in a drop in gas mileage.

Can I still drive?

While the P0451 code may not severely impact your vehicle performance or drivability, it could result in your vehicle emitting harmful fuel vapors into the atmosphere.

Additionally, the error code P0451 may appear alongside other more serious OBD2 codes, so you should have a certified technician check your vehicle.

P0451 causes

The EVAP system is complex, meaning several factors could trigger the P0451 code. 

Here are some common causes:

• Damaged, loose, or missing gas cap
• A malfunctioning fuel tank pressure sensor
• The fuel tank pressure sensor or vapor pressure sensor valve is clogged 
• An open or shorted gas tank pressure sensor circuit
• Damaged or broken charcoal canister, rubber hoses, or gas tank
• A faulty Engine Control Module

Diagnosis

Diagnosing the error code P0451 requires thoroughly inspecting all the components, including the wiring harness, fuel cap, vacuum hose, etc. So, if you’re unsure, it’s best to consult a certified ASE technician.

Here’s how your mechanic would diagnose the code P0451:

1. Begin the inspection using an OBD2 scan tool to identify all the engine codes stored in the Engine Control Module. 
2. Then, clear the Check Engine Light and all the stored codes, do a test drive and see if the Check Engine Light or the engine code resurfaces.
3. If the fault code P0451 or other codes reappear, resolve the DTC P0451 and move to the other engine codes.
4. Then, inspect and repair any damaged, corroded wire or wiring harness in the fuel tank pressure sensor circuit.
5. Next, check the charcoal canister, purge valve, gas cap, rubber hoses, and other EVAP system components.
6. Clear the code and check if the issue is resolved.

Note: When you remove the gas cap, the pressure sensor must fall to atmospheric pressure. Failing to do so could mean the sensor is blocked or clogged.

Possible repairs for P0451 & Costs

In most cases, the repair procedure for error code P0451 means replacing or cleaning the gas cap. That said, here are some other common fixes:

• Fix a faulty fuel tank pressure sensor
• Repair the EVAP canister damage or replace it 
• Clean, repair or replace a damaged fuel tank or purge vent valve
• Repair or replace loose or faulty sensor wiring or connector 
• Repair or reprogram a malfunctioning Engine Control Module

Repair costs

The labor and diagnostic costs for fault code P0451 range from $125 to $160.

The replacement parts could cost anywhere from $20 to $350, depending on the underlying issue and vehicle make and model.

Here are the average estimated costs of the replacement parts:

• Fuel tank cap: $20 to $60

• EVAP line: $20 to $100

• EVAP system pressure sensor: $280 to $300

3 P0451 FAQs

Let’s explore some of the most frequently asked queries and responses about a faulty fuel tank pressure sensor: 

1. What Tools Are Required To Diagnose Fault Code P0451?

In most cases, you only need an OBD2 scan tool and a flathead screwdriver to diagnose the fault code P0451. 

2. What Are The Other Related Evaporative Emission Trouble Codes?

Other more severe engine codes usually accompany the fault code P0451.

These include:

• P0450: Evaporative Emission Control System Pressure Sensor Malfunction
• P0452: EVAP System Pressure Sensor Low Input
• P0453: Evaporative Emission Control System Pressure Sensor High Input
• P0454: EVAP System Pressure Sensor Intermittent
• P0455: Evaporative Emission Control System Leak Detected (Gross Leak)
• P0456: Evaporative Emission System Small Leak Detected
• P0457: Evaporative Emission Control System Leak Detected
• P0458: Evaporative Emission System Purge Control Valve Circuit Low
• P0459: EVAP System Purge Control Valve Circuit High

3. Does The Code P0451 Apply To All Vehicles? 

Yes, the diagnostic trouble code P0451 applies to all OBD2-equipped vehicles, including top brands like Ford, GMC, Audi, Toyota, etc.