Code P0446 EVAP System Check Engine Light

[harringtondav]

Sounds like a good find - the Green wire is the VREF - Signal Return circuit.

Yea, I kinda saw this coming. I mustered enough gumption to get my creeper and check the canister vent valve and cable. ....looking for mouse chewing. The cable sheath was damaged but as far as I could peel it back the green and other wire looked OK.
...still a bit stiff from the surgery, but I reckon by next spring I'll be able to properly dig into most future issues. As a member of the Church of DIY, I'd rather eat a bar of soap than pay someone for something I can figure out and fix.

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[rrwhitman]

Hi everyone,

Check engine light yesterday - code P0451. When the truck was still under warranty I had a check engine light (don't recall the code) and was told it was a hose associated with the fuel tank evaporation system and that the tank had to be emptied and dropped to fix. What are people's ideas on how to proceed with this myself? The purge valve near the engine seems trivial to replace and I've read that the fuel tank pressure sensor can be done without actually dropping the tank. Thoughts? Thanks!

p.s. I do perceive that the engine is not quite as smooth at idle as previously.

 

[RangerBill]

Hi everyone,

Check engine light yesterday - code P0451. When the truck was still under warranty I had a check engine light (don't recall the code) and was told it was a hose associated with the fuel tank evaporation system and that the tank had to be emptied and dropped to fix. What are people's ideas on how to proceed with this myself? The purge valve near the engine seems trivial to replace and I've read that the fuel tank pressure sensor can be done without actually dropping the tank. Thoughts? Thanks!

p.s. I do perceive that the engine is not quite as smooth at idle as previously.

Here is info from the shop manual:

P0451 - EVAP System Pressure Sensor / Switch A Circuit Range / Performance

Description:

This DTC sets when a fuel tank pressure (FTP) sensor range (offset) concern is detected. The FTP sensor output is offset by greater than 1.7 inches of water or less than -1.7 inches of water.

Possible Causes:

• FTP circuit intermittent open
• FTP circuit intermittent short
• FTP sensor intermittent open
• FTP sensor intermittent short
• Contaminated FTP sensor
• Damaged FTP sensor

Diagnostic Aids:

With the FTP sensor at atmospheric pressure, the FTP PID normally indicates 0 inches of water. Remove the fuel filler cap or, for vehicles with a capless fuel filler pipe, install the supplemental refueling adaptor provided with the vehicle to open the capless fuel tank filler pipe. After installing the supplemental refueling adaptor or removing the fuel filler cap, wait one minute to allow the pressure in the fuel tank to equalize with the ambient air pressure before accessing the PID.

Fuel Tank Pressure Sensor and Tube

Removal

NOTE: Removal steps in this procedure may contain installation details.

1. Remove the fuel tank.
   Refer to: Fuel Tank (310-01 Fuel Tank and Lines - 2.3L EcoBoost (201kW/273PS), Removal and Installation).

1. • Disconnect the electrical connector.
   • Disconnect the quick connect couplings.
     Refer to: Quick Release Coupling (310-00 Fuel System - General Information - 2.3L EcoBoost (201kW/273PS), General Procedures).
   • Detach the clip and remove the fuel tank pressure sensor and tube.

Installation

1. To install, reverse the removal procedure.
   

​

 

[rrwhitman]

Thanks, Bill. I've read that you can lower the tank enough to do this and not totally remove it. Do you know if that is true? Also, the links on removing the fuel tank and the quick release fittings - can you expand on those links and post as well? Many thanks!

 

[RangerBill]

Thanks, Bill. I've read that you can lower the tank enough to do this and not totally remove it. Do you know if that is true? Also, the links on removing the fuel tank and the quick release fittings - can you expand on those links and post as well? Many thanks!

I don't know, it might be possible. I have heard that if the truck had undercoating applied, that the undercoating material will get sprayed into the sensor and clog it, causing the code.

 

[DukeCanBuildit]

Here is info from the shop manual:

P0451 - EVAP System Pressure Sensor / Switch A Circuit Range / Performance

Description:

This DTC sets when a fuel tank pressure (FTP) sensor range (offset) concern is detected. The FTP sensor output is offset by greater than 1.7 inches of water or less than -1.7 inches of water.

Possible Causes:

• FTP circuit intermittent open
• FTP circuit intermittent short
• FTP sensor intermittent open
• FTP sensor intermittent short
• Contaminated FTP sensor
• Damaged FTP sensor

Diagnostic Aids:

With the FTP sensor at atmospheric pressure, the FTP PID normally indicates 0 inches of water. Remove the fuel filler cap or, for vehicles with a capless fuel filler pipe, install the supplemental refueling adaptor provided with the vehicle to open the capless fuel tank filler pipe. After installing the supplemental refueling adaptor or removing the fuel filler cap, wait one minute to allow the pressure in the fuel tank to equalize with the ambient air pressure before accessing the PID.

Fuel Tank Pressure Sensor and Tube

Removal

NOTE: Removal steps in this procedure may contain installation details.

1. Remove the fuel tank.
   Refer to: Fuel Tank (310-01 Fuel Tank and Lines - 2.3L EcoBoost (201kW/273PS), Removal and Installation).
2. • Disconnect the electrical connector.
   • Disconnect the quick connect couplings.
     Refer to: Quick Release Coupling (310-00 Fuel System - General Information - 2.3L EcoBoost (201kW/273PS), General Procedures).
   • Detach the clip and remove the fuel tank pressure sensor and tube.

Installation

1. To install, reverse the removal procedure.
   

​

Hey Bob, is there a strong case for why most/all of that (pump incl.) couldn’t have been designed to be mounted on the side of the tank, rather than the top?

 

[RangerBill]

Hey Bob, is there a strong case for why most/all of that (pump incl.) couldn’t have been designed to be mounted on the side of the tank, rather than the top?

I would guess that it is easier to seal the pump to the tank at the top. The pressure sensor would have to be in the air above the tank so no liquid would enter it, so again mounted at the top of the tank.

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