CitznFish

Hello,

I have a 2004 (4.6L) F150 Heritage edition. I recently received a CEL for P0543 Evaporative Emissions Control System Pressure Sensor High Input.

I went to test the Fuel Tank Pressure sensor and it snapped in half, lol. I have replaced this sensor with a new unit but still have the error code. I am not sure where to check next.

Truck idles smoothly and starts without issue.

Also, replaced old cracked gas cap but I can't imagine that has anything to do with this.

TIA,
CF

F150Torqued

About the only thing(s) that can cause P0453 (EVAP Pressure Sensor/Switch High) are defective Fuel Tank Pressure Sensor, or electrical circuit problem in wiring. IE: Open on certain wires or short between certain wires between sensor and PCM. Otherwise it would take TWO simultaneous problems, -Failed EVMV (Evap Vapor Management Valve- {Purge Valve} failure) ANd Canister Vent Valve STUCK CLOSED or clogged charcoal canister.

That would allow heating and fuel evaporation fumes to build pressure in the tank. /// Have you noticed a 'WHOOSH' sound when you remove the gas cap???///

Perhaps the wiring diagram will help sort out wiring problems, with the following references from my 'working' Evap system.

FTP sensor voltage at ZERO pressure/vacuum (neutral - Gas Cap OFF) should be 2.62 volts referenced to vehicle ground. That goes down with negative pressure (when PCM opens EvMV valve) to about .5v at minus 20 Inch Hg. AND UP (HIGH - {which is your problem}) as internal tank 'pressure' rises - up to 5 volts max at ??IDK - pressure.

CitznFish

Thanks for your reply, this is helpful. There is definitely no "wooshing" sounds when I unscrew the gas cap. I wish Torque Pro showed the voltages but apparently it isn't provided by my trucks ECM. So if there is no wooshing and the FTP sensor was just replaced (assuming it isn't a bad replacement) I guess I need to look for a short in the wiring?

as a side note..i did drive about 10 miles with the gas cap off just to see if that changed any of the issues but it just left the same error codes P0453 as stored and pending.

F150Torqued

I just clicked to the 'FACT' that your truck is Heritage model. The schematic is for my New Body Style 2004. Be aware / suspicious of any discrepancies in pin numbers and/or wire colors - as I have NO IDEA how reliable it might be.

I have isolated / identified a bunch of PIDs for parameters and sensors responsible for the EVAP MONITOR system and created a GREAT Torque Pro dashboard for diagnosing the EVAP system. Unfortunately, for the above reason - and the unfortunate NON-STANDARD nature of OBDII PID assignments - it may not be much help to you.

I have been getting ready to post it in a HOW TO thread. I will try to hustle up and get it done. If you are familiar with importing PIDs via a 'csv' file, it might be helpful.