P0455 inquiry - 986 Forum - The Community for Porsche Boxster & Cayman Owners

I've done a fair share of reading about this code, and my circumstance may have occured to others and someone might have insight on how to correct it. Last Friday... Saturday I drove away from the pump... with the nozzle resident in the filler tube. I heard the plastic hose rub against the car, immediately stopping. Hose disconnected at the nozzle, but remained hanging by the two small tubes inside the primary hose. Anyhow... I removed the nozzzle, came right out. However, I noticed that the filler tube housing (?) (the metal hole in which you place the nozzle... the surrounding metal "housing" slight was ajar, ever so slightly "tourqued", "pulled" towards the rear of the car. Surprise! The same direction the nozzle was headed when I pulled away fron the pump. I can see it, but it is slight. Anyhow... before I begin taking the wheel liner off, getting all up in her... I'm wondering if anyone has been through this, or might recommend an order in which I should examine. I don't have a smoke machine. To compound the problem... my running out of gas fiasco which led me to look into the tank (empty) has left the car with a gas smell. It wafts. I returned to the sleeve above the fuel sending unit... removed it... also noticing a small pool of gas atop it... then tightned it to the point where the dab of old glue aligned with where it was before I forst removed the sleeve. Got the sleeve all snugged up... snapped the fuel lines back on... sealed her up... and the smell remains. Once I have some direction on the P0455 matter I'll examing the fittings on the sending unit... thinking maybe something is cracked. Thanks, fellas.

P0455 indicates a large fuel tank ventilation leak, considering the problem with the fill hose, you may have dislodged one or more connections between the fill tube and the EVAP system.

Quotes source post: 655590

Thank you, JFP. I'll do more reading on those connections... the hoses... pull the liner and examine. Hopefully it'll be obvious if something is disconnected. I'll pull and wiggle. Thanks, again!

Doing a smoke test would be quicker..................

Quotes source post: 655592

I agree. I'm either going to make one or buy one. That, and some reading. Thank you, JFP. Your wisdom is appreciated.

Wanted to conclude... Last weekend decided to replace the fuel tank rubber sleeve... the one I'd been sitting on for months, and with that occasional waft of fuel and ever-resident CEL... denoting the P0455 code. Removed the two fuel connections... the vent tube... and electrical connector. Removed the lock ring... that can be a bugger... and used a pry bar to encourage it out. Pulled up the fuel pump/sending unit... a couple/few inches... and there was the original (or however old it was, not replaced in the 6.5 years I've owned it, rubber sleeve. (Porsche Sealing Ring for Fuel Tank Level Sensor Uro Parts 1J0-919-133 A Pelican Parts site). Anyhow... That ring had somehow become dislodged for it was resting, askew, above the sending unit/pump appliance. Clearly that was from where the wafting originated. Since I had to remove the battery the P0455 was cleared, no biggy. I've since driven it ~100 miles... 10 drive cycles or so... and no code has emerged. The OBD2 reader I carry reveals no pending. I discovered that installing that rubber ring first into... atop the tank made for an easier reinstall of the unit. I had installed the rubber ring onto the unit... then attempting to snug it into the top of the tank. That didn't work... for ridiculous while. With the rubber ring first installed into/atop the tank... the unit slid right in. Thankfully it didn't, or hasn't yet again sprung the P0455 code. If it pops up I know I'll then have to begin looking at the fuel filler tube on down. Evap country. Then the smoke test, and an update.

Update: The P0455 code did resurface... I believe within a week oof my last post. I'd been sitting on diagnosing/repairing it because: 1. Smog isn't due until next July. 2. I'm a procrastinator. I had removed the wheell liner, and a visual inspection revealed nothing. So, I sat on it. However, a couple weeks ago I was thinking, "I put on a new Porsche cap... code remained. What if there's a leak at the TOP of the filler tube?" There is a rubber seal that sits just below the top of the filler tube, and mine seems a little loose, kinda just hanging there... never thought much of it. Anyhow... station nozzle stresses the filler tube (a little)... maybe it is "off" just enough that a new cap wouldn't fix the code. So... I took some Gorilla Tape (~3/4 - 1 inch wide and gave it one wrap around thhe top of the filler tube. The top of the tape stting just level with the top of the tube. Screw back on the cap... clear the code and... 2 weeks later and at least 20 start/stop/drive cycles later... the code has not returned. So... then I'm thinking that there light be some sort of sseal/gaasket/part that I'm missing and I start poking around. Here are a couple/few I pulled up... and wondr if soomeone might chime in on which route I should take. https://www.pelicanparts.com/More_Info/99720194400OEM.htm?pn=997-201-944-00-OEM&bt=Y&fs=0&SVSVSI=986M https://www.eurospares.com/Parts/191201557/Porsche?pi=28780 https://www.pelicanparts.com/More_Info/99620175300.htm?pn=996-201-753-00-OEM If these are the wrong parts... what would be the correct part, if one exists? For now I'm going to stick with the tape and... I may remove it for a while to see if the code resurfaces. Any advice appreciated. Thanks!

I knew I should have let sleeping dogs lie. Maybe my luck could have carried me through the July 2025 smog test. Anyhow... code reemerged. Smoke test planned... by June 22025.

So smoke test the Boxster after about 250 generations? That's what I call positive thinking! Hopefully they will still have the necessary equipment ;-)

Quotes source post: 663284

Those errors signal it's time to clip my nails. Or paint them.

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Hey Starter986, I've been having this same recurring issue with my 986 (same year as yours ). I've replaced the fuel pump, that seal ring you were talking about, the bleeder valve on the filler neck, changed out the gas cap, even the regen valve on the throttle body, and I've also done a smoke test. Nothing. The CEL for P0455 still comes back every time after a little while. Smoke test came up empty. Did you ever get a chance to do a smoke test? Or were you ever able to solve the issue?

My code comes on about once a year but I only drive my 98' in the summer and only drive it for about 4,000 to 5,000 miles. The car runs great so I just clear the code and that takes care of it for another 4-5,000 miles. Best news for me is that Illinois no longer requires emission testing once the car is 25 yrs old and wears a "Expanded Antique" license plate. (..and at a reduced price of $51/yr rather than $150/yr)

Quotes source post: 655593

Hmm, I have a smoke machine..