Today, my 2017 F150 Ecoboost 2.7 threw a CEL while I was at the bank drive thru. I noticed the light and heard what sounded like an air compressor. I shut the engine off and the sound went away. I started it back up and the CEL was out and the sound was still gone. I scanned the OBD with my meter and it reported P1450, Unable to Bleed Up Fuel Tank Vacuum.

Research identified P1450 - Unable to Bleed Up Fuel Tank Vacuum

Description:

This DTC sets when the evaporative emission (EVAP) running loss monitor detects excessive fuel tank vacuum with the engine running, but not at idle.

Possible Causes:

• EVAP purge valve stuck open
• Blockages or kinks in the EVAP canister tube or EVAP canister purge outlet tube between the fuel tank, the EVAP purge valve and the EVAP canister
• Fuel filler cap stuck closed, preventing vacuum relief (if equipped)
• Capless fuel tank filler pipe damaged, preventing vacuum relief (if equipped)
• Contaminated fuel vapor elbow on the EVAP canister
• Restricted EVAP canister
• EVAP canister vent valve stuck partially or fully closed
• Plugged EVAP canister vent valve filter
• VREF circuit open

Could any of those problems sound like a compressor?

 

When the EVAP purge valve opens while the engine is running, this allows the engine to ingest the fuel vapors stored in the EVAP canister. If there is a restriction somewhere in those lines, I guess it is possible for the vacuum generated by the engine to create a compressor like noise as the air passes though that restriction.

There are several valves that control the EVAP system. Any one of them could have got stuck partially open resulting in the noise. There could be a kink in one of the lines, but this is unlikely as those lines are fairly rigid (although they are plastic).

The restriction could be in the EVAP canister itself it is saturated with liquid gasoline. With the capless fuel filler system it is important to not "top off" the tank during a fuel fill. Doing so can over fill the fuel tank and fill the vapor purge lines with liquid gasoline. This then flows into the EVAP canister and super saturates the charcoal substrate in the canister. The end result is an EVAP system that is not functioning properly resulting in a CEL.

Do you "top off"? Even if you don't, the problem could be the canister itself.

 

Where is that canister located? I have been getting P06AG, P0454 and P0451 in the past.

 

Here.


Just in front of the fuel tank.

 

Codes 451 & 454 are for the Pressure Sensor circuit.
Hint hint.
Good luck.