Fix P0451: Mechanic’s solutions that WORKED

The code P0451: “Evaporative Emission Control System Pressure Sensor Range/Performance” indicates a problem with the pressure sensor in your car’s evaporative emission control system. This system helps reduce air pollution by capturing fuel vapors from the fuel tank and burning them in the engine. When this code appears, it means the sensor that monitors these vapors isn’t working correctly.

P0451 quick overview

Meaning	P0451: Evaporative Emission Control System Pressure Sensor Range/Performance
Is it serious?	Moderately serious as it affects the vehicle’s emissions control system.
Possible causes	– Faulty fuel tank pressure sensor – Damaged or corroded wiring to the sensor – Kinks or blockages in the EVAP system hoses or tubes – Problems with the EVAP canister or vent hose – Incorrect gas cap or fuel tank pressure
How to diagnose?	Inspect FTP Sensor: Check the fuel tank pressure sensor for proper operation and range. Verify Wiring: Ensure the sensor’s wiring and connections are intact and secure. Check EVAP System Hoses: Look for any kinks or blockages in the EVAP system’s hoses or tubes. Examine EVAP Canister: Inspect the EVAP canister and vent hose for blockages or damage. Monitor FTP PID Values: Use diagnostic equipment to check the fuel tank pressure sensor’s PID values. Check for Updates: Ensure the vehicle’s software is up to date, especially after repairs or replacements. Examine Dust Separator: Inspect the dust separator in the EVAP system for blockages.

How to fix P0451 – learn from mechanics

I looked into P0451 service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.

Case #1: Kia

Vehicle Information

• 2000 Kia Sephia LS 1.8L

Issue + Repair History

• MIL (Malfunction Indicator Lamp) on
• Code: P0451 (Evap Pressure Sensor/Switch voltage low)

Suggested Fixes

• Replace the pump module with an OEM part
• Use a different scanner as P0451 may not be a valid code for this vehicle
• Utilize Kia’s online technical site for additional information and guidance

Final Fix

• The issue was an incorrect computer installed in the car, likely from a 1999 or older model
• Replacing the computer with a used one from a 2000 model resolved the code issue
• Noted that there is no fuel tank pressure sensor on the 2000 Sephia, only on 1999 and older models, where it is mounted to the top of the fuel tank sending unit

Case #2: Honda

Vehicle Information

• 1999 Honda Odyssey LX 3.5L

Issue + Repair History

• MIL (Malfunction Indicator Lamp) on
• No drivability complaints; vehicle runs fine

Computer Codes & Descriptions

• P0451 – Evap. pressure sensor out of range

Suggested Fixes

• Check service bulletins for this specific code
• Place an orifice tube in one of the evap hoses as per a bulletin
• Educate the customer on properly tightening the gas cap
• Consider installing a one-way valve as per a bulletin
• Check the fuel tank pressure sensor in the top of the tank

Final Fix

• Cleaned and applied a smear of grease on the gas cap gasket
• This resolved the issue, and the customer had no repeat problems

Case #3: Porsche

Vehicle Information

• 2003 Porsche 911 Carrera 4 3.6L

Issue + Repair History

• MIL (Malfunction Indicator Lamp) on
• Code: P0451 (Tank pressure sensor signal implausible)
• Difficulty locating the fuel tank pressure sensor

Suggested Fixes

• Check under the battery tray for the sensor
• Inspect for chewed wires or a failed sensor
• Ensure a factory fuel cap is installed, as incorrect caps can cause this code
• The sensor is part of the fuel sender/pump cover assembly
• Check for leaks in the plastic cover of the assembly, as this can trigger the code
• Examine the rubber fitting on the filler tube for potential leaks

Final Fix

• Found the sensor beneath the battery
• Replaced the failed sensor, resolving the issue

Case #4: Chevrolet

Vehicle Information

• 2009 Chevrolet Malibu LS 2.4L

Issue + Repair History

• MIL (Malfunction Indicator Lamp) on
• Code: P0451 (fuel tank pressure sensor performance)
• No previous related repair history

Suggested Fixes

• Run diagnostics for the Evap system
• Check if the gas cap is properly tightened
• Consider if the vehicle is still under emission OEM warranty
• Inspect for harness damage or bad sensor
• Check if there are any other codes indicating an EVAP leak test issue
• Replace purge valve if found faulty

Final Fix

• Checked the Evap system, which was operating normally
• Compared the fuel tank pressure (FTP) reading with an older model and found it almost identical
• Cleared the code
• No recurrence of the issue after two weeks

Case #5: Ford

Vehicle Information

• 2005 Ford Taurus SE 3.0L

Issue + Repair History

• MIL (Malfunction Indicator Lamp) on
• Code: P0451 (EVAP system pressure sensor range/performance)
• No change in fuel tank pressure sensor readings with various tests

Computer Codes & Descriptions

• P0451- EVAP system pressure sensor range/performance

Suggested Fixes

• Monitor the FTP (Fuel Tank Pressure) sensor PID; should be around 1.7 in-H20
• Check for kinks or bends in fuel vapor hoses/tubes between fuel tank and dust separator
• Inspect the EVAP canister ports and canister vent hose assembly for blockages
• Replace the FTP sensor if the above checks are okay
• Verify wiring integrity, especially voltage and ground at the FTP sensor
• Check for high resistance or open circuits in the wiring

Final Fix

• Replaced the fuel tank pressure sensor assembly, which resolved the issue

Advice	Diagnostic Step Description
Inspect the Fuel Tank Pressure Sensor	Check the FTP sensor for proper operation and readings, and replace if out of range.
Verify Sensor Wiring and Connections	Examine the wiring to the FTP sensor for any signs of damage, corrosion, or disconnection.
Check for Kinks in Fuel Vapor Hoses/Tubes	Inspect hoses and tubes in the EVAP system for any kinks or bends that could impede flow.
Inspect EVAP Canister and Vent Hose	Look for blockages, contamination, or debris in the EVAP canister and vent hose assembly.
Monitor FTP PID Values	Use a scanner to monitor the Fuel Tank Pressure sensor’s PID values to verify proper operation.
Check for Software Updates or Recalibration Needs	Ensure the vehicle’s software is up to date and consider recalibration if necessary after repairs.
Examine Dust Separator for Blockage	Inspect the dust separator in the EVAP system for any signs of blockage that could affect pressure readings.