2002 V6 - P0455 code

Absolute first thing. Check the gas cap.

Next check the grommet sealing the filler neck to gas tank seal. As these cars age, the grommet cracks and leaks. Gas is hard on rubber parts. Typically this results in a gas leak as the car is filled.

Then inspect the gas filler neck itself. Esp under the plastic "guard". Sometimes water/salt will collect under the plastic and rust out the filler neck.

Next check the vapor lines in the engine bay. Follow the EVAP vapor line from the rear TB area back under the right hand fender well. Look under the car for damage.

Pay special attention around the gas tank and by the charcoal canister. Inspect the lines looking for disconnected or damage. The charcoal canister is located next the gas tank behind the left wheel.

The P0455 indicates a LARGE leak so we are not looking for pin point holes here. This is further back up by the fact you can SMELL gas. If you still can't find it, look around. Use your nose. Has anything else changed?

OBTW, looks like the new PCM got you back on the road. Please consider updating the original post with final resolution and "lessons learned" so that others can benefit.

wmburns said:

Next check the grommet sealing the filler neck to gas tank seal. As these cars age, the grommet cracks and leaks. Gas is hard on rubber parts. Typically this results in a gas leak as the car is filled.

Click to expand...

Recall that the gas tank grommet was the 2nd thing to check.

A new grommet is less than $20 from Ford. It is a common problem on older cars.

The Mustang has one of the easier tanks to drop. It took me less than 1 hour to drop the tank on my 2000. Only a few hand tools and a floor jack is required. It is important to run the tank as close to empty as possible. Remember to completely cut away the old grommet before removing the filler neck. Otherwise, the anti-rollover valve on the end of the filler neck will be damaged. It can not be serviced (new filler neck).

There are tons of how to articles regarding dropping a Mustang tank.

Good luck if you decide to do the work yourself.