I have had a P0455 code with check engine light on. I changed the fuel cap, reset the light, but it came back after a few days. I changed the Purge Valve, reset the light and the light came back on after a few days. So, I removed the new purge valve and reinstalled the old one. Next, I changed the Purge Valve Solenoid, reset the light and again after a few days, the light came back on. So, I removed the new Purge Valve Solenoid and installed the old Purge Valve Solenoid. Next, I had someone to run the smoke test in the lines and they did not find any leaks in the lines. My last action was to change the Charcoal Canister. I did so and the light came back again. Any guidance will be appreciated.

 

Welcome to the forum

P0455 Evaporative Emission Control System Leak Detected (gross leak)

The "Gross Leak" is the important part

Never Google a code you will get misleading info, look up codes in a full list like this one: https://www.therangerstation.com/tec...II_codes.shtml
Then you can see ALL the codes the computer could have used, which can help you eliminate some things, and why the computer used that one code, instead of others

Most likely the fuel filler hose or Vent hose is the issue

Easy test for EVAP leaks
get a hose and a damp towel, and a helper with good lungs, lol
Take off gas cap and put hose in filler
Wrap damp towel/rag around the hose and hold it in place to SEAL the gas tank
Have helper Blow into the hose while you listen for air escaping
I am sure you will hear it at the gas tank, but you can check engine bay as well

DO NOT use an air compressor for this test, YOU WILL BLOW OFF fittings
Human lungs can generate about 2psi pressure so no fittings will be in danger of blowing off

 

I took it to a shop for a leak check and they did not find any leaks. Wouldn't your suggestion about checking for air escaping (using a hose and damp towel) showed up in the leak test?

 

Yes, it would show up easily if they were testing the gas tank

So if Computer is still setting the P0455 then the pressure sensor on the tank is bad, which should set its own code

P0450 Evaporative Emission Control System Pressure Sensor Malfunction
P0451 Evaporative Emission Control System Pressure Sensor Range/Performance
P0452 Evaporative Emission Control System Pressure Sensor Low Input
P0453 Evaporative Emission Control System Pressure Sensor High Input
P0454 Evaporative Emission Control System Pressure Sensor Intermittent

Or computer has a bad internal circuit or software glitch

Pressure sensor should be on the top of the gas tank in 2003 but not sure, if you overfill the gas tank then over time it will damage this sensor, its possible its just clogged up so pressure is not changing inside its diaphragm, so computer sees the circuit is OK no broken wires, and it sees "a pressure" but its not changing when computer applies a vacuum to the gas tank, so "gross leak" no pressure change at all, "small leak"(P0442) would be a pressure change but doesn't hold very long

If you can remember from previous times of stopping for gas, when you opened the gas cap you would hear a "whoosh" of air noise
Do you still hear that?
That's a sign of the EVAP system working as it should, if you still hear that since the code came up then its a false code

 

I do not recall hearing a "whoosh" of air noise, when opening the gas cap.