P0455 woes

2004 C4S Engine code P0445 P0455 Replaced: -breather valve in engine bay -filler neck breather valve (cured inability to fill up completely) -gas cap I initially noted a completely disconnected hard plastic line to the valve housing. I thought bingo this was the problem but still threw P0455 code after several miles. Bench tested: vapor purge solenoid - passed Multimeter test: vapor purge solenoid connector - passed - I also confirmed activation of the solenoid, via manual ground bypass method, while it was connected to power. FTP sensor three pin connector - passed - I also noted voltage deviation (2.77 to 2.80v) in one of the pins while heavy pushing on the gas cap. I performed the smoke test from the engine bay, with 1 psi, after plugging the vent hose under the car by the transmission. (That is the vent correct?) However I never saw smoke coming out of the fuel fill port with cap off. Normal? I did not see any smoke leak anywhere from inside engine bay, bottom of car, and front passenger wheel well. I did a manual blow test (with my mouth) from the engine bay with the plastic connector connected and disconnected from the charcoal canister noting moderate resistance but i was able to blow. So this leaves me with bad ground wire before the wheel well? What a headache.

I just remembered that when I did the manual blow test I had already unplug the vent hose from under the car by the transmission. Should I redo this test?

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Are you dealing with P0445 or P0455? Both? Or was P0455 a typo?

Ooopppsss great catch! dealing with P0455

Okay, got it, thanks. No P0445... but only P0455.

Any thoughts?

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Remove the battery and battery tray then smoke test the fuel tank ...Look for cracks and smoke from the fuel pump access lid.. After 27 years the fuel pump lid can have cracks in it that can cause the P0455 ... This is becoming an increasing problem but has been a problem for over a decade ...

just did this and i didn't see any leak. man oh man. even took out the charcoal canister gave it a good shake and smoked test passed with flying colors. now what? test the resistance from the DME wire to the EVAP shut off valve wire? sounds daunting besides i don't have that long of a multimeter lead lol

How likely can the DME be the problem? I am leaning more towards a chewed up wire and I can simply run a new one. Better than cloning a new DME.

just tested the continuity from the ground wire of the EVAP shut off valve to the DME wire (Plug 4, pin 30) and its 0 ohms which is good. mmhhh i cannot believe the DME is the problem. i am missing something here.. anyone????

You can test the charcoal canister and see if there is any resistance when you blow into each opening. If there is resistance, then it is blocked up and you need to replace with new or used. You can try and free it up as well to by beating on the sides with a rubber mallet and blowing thru it with an air compressor. If the canister is blocked up it will not flow thru to the purge valve and will not fill easily (lots of clicking when filling). Took me a year to go thru the full system testing every valve to isolate the issue to the canister. The exhaust hose that is under the fender should also be blown out - it can get clogged with who knows what and will create back pressure. Mine clogged a bit, and I blew it out with compressed air to make it flow freely.

Code P0455 is for a leak in the fuel tank or associated hoses/lines. Why don't you do a manual pressure/vacuum test systematically of the fuel tank and/or associated hoses and lines ...See if the tank really can hold a vacuum and also a slight pressure ...

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what would be a good kit for this for either manual pressure or negative pressure? and how much positive or negative pressure can the lines safely endure? I have the quick fill system I used for my coolant, can that be used? Having a good seal on the fuel fill opening seems tricky as I learned doing the smoke test.

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i don�t recall manually blowing through it but the canister did not have anything loose nor was there any powder that came out of the ports when I tap. I suppose I can take it out again and blow through it haha

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Amazon.com: DHA 2 in 1 Hand Vacuum and Pressure Pump Tester Brake Fluid Bleeder Bleeding Kit One Man for Car Motorcycle : Automotive Amazon.com: DHA 2 in 1 Hand Vacuum and Pressure Pump Tester Brake Fluid Bleeder Bleeding Kit One Man for Car Motorcycle : Automotive I would use a hand vacuum/pressure pump like above to test the fuel tank and associated hoses/lines.... It may take quite a bit of hand pumping to get the vacuum/pressure that you want but at least you won't over-pressure it..... I would use less than 5 psi/inhg ... Some hand pumps do vacuum only but this will do vacuum and pressure....

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Perfect thank you sir!

so i did buy the inflatable bladder to have a greater seal on the fuel fill port and ran the smoke test again. (the first time i ran it using just a cone i didn't have a good seal). and again absolutely no evidence of leak. i tried the hand pump to induce positive pressure as recommended but it was taking way too long and my hands were cramping lol. may be the problem is the charcoal canister even though i tested it pretty well with the smoke test, shake test, and no powder residue coming from its ports. i would just hate to replace that and find out i am wrong because its quite expensive. i am at a lost and i need this to go away to pass the smog test for illinois. damn.

Well hell I went ahead bought a 50k miles used charcoal so I�ll see if it fixes it!

Be sure to blow into the various pipe connections to see if you can feel resistance on both the new unit and old unit. My unit that was bad had noticeable resistance when blowing into the port that came from the tank. New (used) unit off ebay had much less resistance and ultimately worked to eliminate codes and fueling issues.

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yup ebay one is noticeably easier. old one was mild-moderate resistance. i shall see with several more miles with it on.

Well that certainly was not the fix by replacing the charcoal as code came back. Frustrating. I am out of ideas. I guess replace the fuel tank plastic neck and rubber since it�s original.

Have you verified that when you insert something into the filler neck that the valves(s) under the fender are both working properly? Also that the vent line out of that valve body is not clogged (that is the vent and runs to the transmission area). It may need to be blown out with compressed air so it is not obstructed. Mine was also rather restricted. Ultimately you will find it (and probably become an expert on this rather bizarre setup). Keep plugging away!

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the vent valve that wraps on the filler neck yes it�s brand new. Additionally the solenoid vent. are you speaking of the vent on the left hand side of the car near the transmission? I can may be blow compress air from the engine side?

I am meaning the valves located in the fender well just to the left of the filler neck. There are two valves in that valve body. One of the hoses from the charcoal canister connects to that valve body. When you insert something (like a socket extension) into the fuel neck you will (should) hear that valve click. Another valve will also click on top of the fuel tank - so you need to listen carefully in the fender (above the tire under the fender liner) for those valves actuating. In that valve body are two solenoids and three hoses. The one on the side (not connected to a solenoid) goes to the transmission area and is just a hose that vents to atmosphere. That hose can get clogged along the way.

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P 0455 fault code denotes leaks of either pressure or vacuum in the fuel tank or its associated lines/hoses. Maybe the reason you could not get the tank to pressurize was because there is a leak somewhere...? If tank can hold 5psi, it will hold vacuum.. If you did get the hand pump/bleeder kit with gauge use it a little differently if you're having a hard time pressurizing the system.... Seal off the fuel tank fill port with a mechanics rubber glove or 2 doubled up if they are real thin. Secure them to the tank filler neck with wire tires or a rubber band. Cut the end off one finger. Or if you have a old fuel tank cap, drill it and screw in a small nipple that fits bleeder pumps hose.. Secure the pump/bleeder testers supply hose to the cut off glove finger or nipple in spare cap, , seal off tight with wire tie. Install the T fitting that comes in the kit into the pump supply hose. Rig up a small hose from your air compressor blow nozzle to the T fitting. Slowly/carefully squeeze the air nozzle trigger to allow only 4-5psi into the fuel tank system. If you have it set up right you should be able to use the gauge on the bleeder pump to see fuel tank pressure. Should be able to pressurize tank using the above method to 5psi max and after it gets there, should hold pressure for at least a while. If it won't hold pressure You might be able to hear the leak if you've got a quite area to do this in. Or use a spray bottle or a small cup with dish soap suds worked up to a froth. Spray or slather on the soap suds froth to all possible leak areas. Once you find the leak(s) they will bubble up big time from the soap suds you slathered on. Spray soap suds on things like fuel tank sending unit hat and its surrounding 'nut ring' its top area that has all the connections. The valves on the tank filler pipes, stuff like that are common leak points... Smoke test might not show up leaks that take more pressure to leak.... Good luck...

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got it about the vent hose. thanks will push air into that!

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I�m gonna do the easy route and bought this it has a gas cap adapter and gauge. Amazon Amazon

ok so it appears a leak is inside this area circled red. i tried using an endoscope to localize it but definitely not helpful. it seems to be rising upward from the bottom area. i think... how do i get inside there? if I remove the filler neck can i get access in there and disconnect each of the three black plastic lines? Its gotta be one those lines. I have small hands lol.

U need to remove the tank to access those lines. If its the fill neck of the tank there is a gasket and people have repaired it without pulling the tank.

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oh dang that seems a big job to remove tank. *****.

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Not as hard as u would think. Think its 8 bolts for the front cross member, 4 bolts on the track along with the steering shaft and tie rod ends, pull battery and disco pump, 4 strap bolts and its out. Of course a lift is the correct tool but it can be done on quickjacks or even jack stands. I would do everything u can to determine if its a pin hole in a small line or the tank to filler seal. U can get to the ends each one of those plastic lines. I would be diconnecting each one, seal one end and smoke test each one.

I suggest that you get a complete understanding of the images below. If you are not smelling gas, I highly doubt you have a fuel filler leak. Most likely one of your solenoid valves/hoses on top of the tank have an issue. You can test those by blowing in the hoses to see if they are completely opening or closing. You need to go thru all the valves to eliminate what is really working and what is not. Valves 2,3,11 and 12 are all triggered by the reed switch in the fuel neck (putting in a socket extension will trigger it). 10(E) is the vent that can get clogged as well. You will need to pull off that and try blowing thru it with compressed air to see if it is clogged. As someone said P0455 is for either Excess Pressure or a Vacuum Leak . The images below are from earlier posts that I pulled together to trouble shoot my system.

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I�ll tackle this weekend! Thank you for advice!

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thank you for placing detailed diagram. I don�t suspect the fuel neck either. But it does appear I have to drop down the gas tank to fully investigate the lines in there.

Ill also add....im pretty sure u dont have to remove the coolant lines thats snake under the car but i cant fully remember. Good luck.

so there i was under the car to plug the exhaust port (red arrow, right side at the end of the transmission body you facing forward) and i see this June bug heading straight for me and landed immediately into my ear hole. holy sh** it was painful as it burrowed. like an alien straight into my brain. i ran inside in a panic telling my dad to get the needle tip tweezer and get the bastard out. thankfully a minute later it figured its way out. wow. had my ears plugged with the tapered rubber the rest of the night. anyways so i decided to repeat the smoke test again to confirm leak was coming from inside the crevice before i proceeded to drop the fuel tank. surprise surprise it was coming from the port of the vapor purge solenoid. for whatever reason i thought i had seen it coming from the crevice the other night. weird. whatever. apparently i had not pushed in the solenoid hard enough to seal when i replaced it. so make sure it clicks in tightly. repeated the smoke and it held 2 PSI. thank goodness. btw i highly recommend smoke tester below (you can now only find it on ebay) as it comes with a psi gauge internal compressor, and a handy fuel port seal disk. i think because i didn't activate the purge solenoid above with a bi directional scan tool that i needed to plug that exhaust port to maintain a psi reading during the test. otherwise your smoke just escapes from there. what a pain this had been.

Glad to hear you're okay!

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Fify Were u able to clear the code?

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I will today and take it for a longer drive to see if it comes back. Should as there is no more leak according to the pressure test.

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still sore 😅 it definitely got my flight response going haha.

No code! yay

Congrats! So in the end what change do you believe solved your issue? - Charcoal canister change or something else?

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the new smoke tester helped a great deal with its pressure gauge and the fuel filler seal that allowed a better smoke test leading to better diagnosis. However I may had replaced a faulty charcoal but then created a new problem by not sitting the purge valve tightly after I placed a new one.

Anddddd of course now I have ABS PSM lights on. Bi directional Scanner tells me �pressure�. Is this the pressure sensor on the ABS hydraulic unit? Or is it a list of other potential sensors? Ie speed sensor? both lights come on after several seconds to minutes of driving not immediately after starting car. I love you 996 but you keep giving to dos!

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You need to make sure your brakelight switch is functioning and adjusted properly ...........The brake lights MUST come on BEFORE the pressure sensor value starts to rise, otherwise it will set the fault ..

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well it was definitely the brake light switch. disassembled the switch, cleaned contacts w/ break cleaner, some scrubbing and all is now well. thanks PorscheTech!

Sharing some steps from Some files,from. A link with workshop manuals I purchased some time ago with lifetime access https://europeancarmanuals.etsy.com Removing the fuel tank on a 996 Carrera 4S is a major mechanical job. Because the C4S features an all-wheel-drive system, the front differential, drive shafts, and front subframe completely block the lower exit path of the tank. Unlike a standard 2WD Carrera, **the fuel tank on a C4S must be dropped out from underneath the car**, which requires stripping the front drivetrain and suspension. ### Critical Safety & Preparation * **Drain the Tank Completely:** Fuel weighs roughly 6 lbs per gallon. You want the tank as empty as possible before lowering it. You can jump the fuel pump relay to pump the gas out via the fuel rail, or siphon it directly from the top access portal. * **Disconnect the Battery:** You will be disconnecting fuel lines right next to electrical connectors. Eliminate all power sources. * **Support the Car Securely:** You will be under the front end applying significant torque to subframe bolts. Use high-quality jack stands on the factory lift points, or a standard commercial lift. ## Step-by-Step Removal Sequence 1. Top-Side Disconnection (Frunk) Requires access to top fuel hat Remove the frunk carpet, plastic battery surround, and the spare tire/inflator kit. Locate the oval access plate held down by 10mm nuts just forward of the battery. Remove the plate to expose the top of the fuel tank sender and pump. Unplug the main electrical harness and disconnect the quick-release fuel supply and return lines. 2. Wheel Well & Filler Neck Disassembly Right-front side Remove both front wheels and the plastic inner fender liners. On the passenger side, unbolt the fuel filler neck assembly from the inner body structure. Disconnect the EVAP lines running from the charcoal canister to the neck, and remove the mechanical vent valve connections so the neck can drop freely with the tank. 3. Disconnect the Steering Column Inside the cabin / lower shaft Lock the steering wheel perfectly straight. Underneath the car near the steering rack, remove the pinch bolt securing the lower steering shaft universal joint to the rack. Slide the joint off. Crucial: Do not let the steering wheel spin freely while disconnected, or you will snap the internal clockspring ribbon cable. 4. Remove Front Axles & Drive Shaft AWD specific infrastructure Unbolt the center longitudinal drive shaft from the rear of the front differential. Unbolt the front CV axle shafts from the output flanges of the front differential. You can hang the axles out of the way with mechanics wire; they do not need to be completely pulled from the wheel hubs. 5. Support and Drop the Front Subframe & Diff Heavy lifting stage Place a hydraulic transmission jack or secure support under the front crossmember/subframe assembly. The front differential can stay bolted to the subframe to save time. Remove the main subframe mounting bolts and slowly lower the entire structural assembly (subframe, differential, steering rack, and lower control arms) straight down. 6. Disconnect Under-Car Shielding & Lines Exposing the tank floor Remove the plastic aerodynamic underbody panels beneath the fuel tank area. Disconnect the lower fuel lines and vent lines running along the transmission tunnel. Unbolt the metal support straps or structural brackets that cradle the bottom of the plastic fuel tank. 7. Lower and Guide the Fuel Tank Out Final extraction With an assistant guiding the filler neck out of the right fender portal, slowly lower the plastic fuel tank assembly out from the bottom of the chassis. Watch closely for any remaining small EVAP vent hoses or wiring clips that may catch on the frame rails as it descends. ### Reassembly Notes * **Aligning the Filler Neck:** When lifting the tank back up, a helper is mandatory to guide the filler neck accurately through the guide hole in the right-front wheel well without tearing the rubber boot. * **Subframe Torque:** The front subframe structural bolts are critical chassis components. Ensure they are torqued strictly to factory specifications, and perform a full 4-wheel alignment once the suspension is reassembled. * **New O-Rings:** Replace the large rubber sealing gasket on the top frunk fuel pump access hat if it shows any signs of flattening or swelling to prevent future EVAP leaks. Removing the fuel tank on a 996 Carrera 4S is a major mechanical job. Because the C4S features an all-wheel-drive system, the front differential, drive shafts, and front subframe completely block the lower exit path of the tank. Unlike a standard 2WD Carrera, **the fuel tank on a C4S must be dropped out from underneath the car**, which requires stripping the front drivetrain and suspension. ### Critical Safety & Preparation * **Drain the Tank Completely:** Fuel weighs roughly 6 lbs per gallon. You want the tank as empty as possible before lowering it. You can jump the fuel pump relay to pump the gas out via the fuel rail, or siphon it directly from the top access portal. * **Disconnect the Battery:** You will be disconnecting fuel lines right next to electrical connectors. Eliminate all power sources. * **Support the Car Securely:** You will be under the front end applying significant torque to subframe bolts. Use high-quality jack stands on the factory lift points, or a standard commercial lift. ## Step-by-Step Removal Sequence 1. Top-Side Disconnection (Frunk) Requires access to top fuel hat Remove the frunk carpet, plastic battery surround, and the spare tire/inflator kit. Locate the oval access plate held down by 10mm nuts just forward of the battery. Remove the plate to expose the top of the fuel tank sender and pump. Unplug the main electrical harness and disconnect the quick-release fuel supply and return lines. 2. Wheel Well & Filler Neck Disassembly Right-front side Remove both front wheels and the plastic inner fender liners. On the passenger side, unbolt the fuel filler neck assembly from the inner body structure. Disconnect the EVAP lines running from the charcoal canister to the neck, and remove the mechanical vent valve connections so the neck can drop freely with the tank. 3. Disconnect the Steering Column Inside the cabin / lower shaft Lock the steering wheel perfectly straight. Underneath the car near the steering rack, remove the pinch bolt securing the lower steering shaft universal joint to the rack. Slide the joint off. Crucial: Do not let the steering wheel spin freely while disconnected, or you will snap the internal clockspring ribbon cable. 4. Remove Front Axles & Drive Shaft AWD specific infrastructure Unbolt the center longitudinal drive shaft from the rear of the front differential. Unbolt the front CV axle shafts from the output flanges of the front differential. You can hang the axles out of the way with mechanics wire; they do not need to be completely pulled from the wheel hubs. 5. Support and Drop the Front Subframe & Diff Heavy lifting stage Place a hydraulic transmission jack or secure support under the front crossmember/subframe assembly. The front differential can stay bolted to the subframe to save time. Remove the main subframe mounting bolts and slowly lower the entire structural assembly (subframe, differential, steering rack, and lower control arms) straight down. 6. Disconnect Under-Car Shielding & Lines Exposing the tank floor Remove the plastic aerodynamic underbody panels beneath the fuel tank area. Disconnect the lower fuel lines and vent lines running along the transmission tunnel. Unbolt the metal support straps or structural brackets that cradle the bottom of the plastic fuel tank. 7. Lower and Guide the Fuel Tank Out Final extraction With an assistant guiding the filler neck out of the right fender portal, slowly lower the plastic fuel tank assembly out from the bottom of the chassis. Watch closely for any remaining small EVAP vent hoses or wiring clips that may catch on the frame rails as it descends. ### Reassembly Notes * **Aligning the Filler Neck:** When lifting the tank back up, a helper is mandatory to guide the filler neck accurately through the guide hole in the right-front wheel well without tearing the rubber boot. * **Subframe Torque:** The front subframe structural bolts are critical chassis components. Ensure they are torqued strictly to factory specifications, and perform a full 4-wheel alignment once the suspension is reassembled. * **New O-Rings:** Replace the large rubber sealing gasket on the top frunk fuel pump access hat if it shows any signs of flattening or swelling to prevent future EVAP leaks.

Well shoot thank goodness I avoided that!

well after less then 30 miles the code came back. I am beginning to feel my 996 thinks i am not having enough fun... Did the smoke test again and found a leak on the passenger side of the engine bay --- i think under the intake manifolds. Is this line connected to the regeneration valve?

The 3mm vac line that goes over to that side is connecter to the fuel pressure regulator.

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I don�t think that line can cause a p0455 code? I did the smoke test from the fuel fill.

Hard to see where the smoke is coming frim. Might be the fuen line vent above the trans?

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i think your right it might just be coming from the atmospheric vent line (red circle) and making its way upward on engine bay. Mmhhh I think I may had been doing the entire smoke test all wrong�.i previously plugged this atmospheric vent line but instead I should just command the purge valve solenoid close, correct? as a side note there is a hole on the far right wall of the fuel fill bay (not the spillage hole). Does this need to be plugged or will commanding the purge solenoid close is what�s necessary?

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Sorry rehash this but �E� is the one that I need to disconnect from this hub and blow compressed air through to clean potential debris? This is the same as the atmospheric vent line. and I believe �D� is the one I am referring to above where it sits to the far right wall in the fuel fill bay. going back to properly performing the smoke test. I think I�ve really confused myself. But to finally put this to bed what I need to do is plug the end of the�D� line and the port where �E� is connected to? Correct? Therefore I don�t need to command the purge solenoid close.

ok, i reconfirmed there is no leak...maintained at 1 psi after an hour. i also blew compressed air towards the atmospheric vent line (line "E") as previously been suggested to clear any debris. i've replaced: -breather valve in engine bay -filler neck breather valve -gas cap (a year ago) -solenoid purge valve -charcoal canister FTP sensor passed the bench test before. i am so out of idea at this point. maybe time to take it to professional --- ugh

Hi Carlo, Did you verify that the solenoid valves F and G are working? Also, which way did you blow compressed air for the vent line? From E connector to the vent exit? It should be checked from E to the exit. All the solenoid valves in the system need to function properly for this system to work. If one is not working, you will get an error. I had to check both F and G by disconnecting the electrical connectors and applying 12 volts (9 volt battery will do as well) to make sure they were both working and actuating the valve. This will eliminate them (or not) as a failure point. You also need to blow air thru them to make sure that the valve body is working (and not just the solenoid making noise). As I stated previously, you need to eliminate what is working correctly to find the problem. Unfortunately, it will always be the last in the system. You also need to eliminate the valves on top of the tank - I have a C4 as well. and you will need to feel for the one that is not able to be checked easily (#6). Meaning it is not accessible unless you drop the tank. It will actuate when a gas nozzle is inserted into the neck. You will need to listen for that valve to open and close inside of the frunk. You should be able to feel/hear it actuate just to the left of the battery area (toward the front of the car a bit). You will need to learn to listen/feel for the different valves actuating to really tell if they are opening/closing when inserting something (like a socket extension) into the fuel filler neck. Keep going. You will figure it out.

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I replaced G w/ new solenoid but never considered to check on F --- i'll do that tonight. tbh i didn't even think about that as i was focused on G and didn't even consider F to be like G dohh blew from E to exit #6 --- referring to the black and white diagram thats pointing to something on top of the charcoal canister? can you give me a part number to refer to its appearance? ill do the extension socket trick to hear for this. did i miss something? i considered replacing the fuel pump seal and collar but that passed the smoke test.

checked F and bench test is good -- opens with voltage. closed w/o voltage with the blow test. the solenoid in the frunk also actuated on and off with the extension socket trick. now what? haha

So if you are still throwing the code it will be one of the component in the green circuit. You seem to have eliminated all the solenoids and the mechanical valve on the fuel neck, so I would say the only thing left is the charcoal canister as the likely culprit (as it improved, but didn't eliminate the code). Does you charcoal canister have all 3 ports on top? (some have a port on the bottom). I made a 3d printed canister (basically a manifold) to see if my canister was bad, but never got to try it out as my cheap used one worked. I could post that for you to try if you have a printer. I have made so many replacment parts that it is an invaluable shop tool at this point.

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the canister have three ports at the top exactly as the original. The blow test on the replacement was without restriction, and had no loose internals. It seems to be a pretty solid non defective replacement part. But you�re right it could also be defective. I was hoping to perform an evap system test with my Autel scanner but sadly no option. I just gotta drive it again and hope for the best. Ugh

Are you sure you are dealing with code P0455 and not code P0445 ? Code P0455 can have two different " sub-codes" if using PIWIS ....Sub-code 1 is " below limit " which means there is a leak somewhere in the system......sub-code 2 is " signal Implausible " which means the Pressure Sensor signal is unbelievable and the pressure sensor should be replaced... With a PIWIS you can also run the "Short Test " to test the system quickly without having to drive it for a long time......You can also monitor the Pressure Sensor Signal in real time and Log it to see if there is an anomalies in the Signal..

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yup 455 😅 ok I just look up the whole PIWIS and will set up one from your previous post. Thanks! It may indeed be FTPS issue however the bench test was unremarkable. Now just gotta set all this up. Unless there is someone near Batavia, Illinois with this setup? 😬

Bought the doggle waiting for shipment. Hopefully it�s just the FTPS. In mean time I replaced the tank rubber neck collar and plastic securement thingy 😅

found out the PIWIS is not compatible on the M3 macbook air. Went ahead bought a cheap well used dell latitude laptop on ebay.

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I did tHe same with an thinkpad and have it dedicated so it boots right into the piwis program.

Piwis up and running. Waiting for doggle to arrive Monday. Had ran car 50 miles without code but maybe it just haven�t met criteria to run evap test.

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@Carlo D can you help me understand how you are running the evap smoke test? I am using the same smoke tester you linked above but I don�t have a gauge. Reading up on it has me a little confused about whether or not I�m supposed to block off a line that vents to the atmosphere or not. I didn�t block off anything yesterday, ran the smoke tester from the fuel filler with the tool to hold the flap open and couldn�t find any leaks. Pulled off the line going into the purge valve and eventually saw smoke coming out of there, so I know it was at least getting through the system. I can also smell fuel fumes once in a while when the tester is hooked up, as if it�s pressurizing the system a bit and a relief valve is venting to the atmosphere but it seems like it opens and closes intermittently.

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Disconnect E and plug the port from where you disconnected with a rubber stopper. Similarly trace D and it leads to the right side wall of the fuel fill bay -- plug the port with a rubber stopper. Then run the smoke test. Otherwise the smoke just vents to the atmosphere. The smoke device with the gauge is no longer sold by the company. The gauge was helpful for me to make sure it could hold pressure = no leak (instead of looking for a smoke). For you you have to just look for the smoke.

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Thanks! Are you using the tool to hold the flapper open and filling from the gas cap adapter?

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sure am! That helps seal it for sure.

well PIWIS gave me a "below limit value".. i really don't get it as my pressure test had been able to maintain 1 psi and no detectable smoke leak. if it�s the FTPS then I should had gotten the signal implausible or not necessarily?

Tried looking for �tank pressure� under Actual Values couldn�t find it.

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Did you use the "arrows" on the right side to scroll through the whole menu ?

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yea absolutely. using key word search for fuel or tank or pressure did not return what i need. baffling.

Well, it been 20 years since I have dealt with this particular issue, and it was PIWIS 1 System, so maybe the " Porche Engineering nomenclature " was changed for PIWIS 3 , that happens all the time with Porsche.. Do this :: Group all those " tank pressure xxxx" values together and screenshot them.. Then disconnect the tank pressure sensor and screenshot them again.. then reconnect the sensor and pull a slight calibrated vacuum and screenshot it then put a light calibrated pressure on the tank and screenshot it post all that here for me..with that we can figure out what those values mean.......but with the " Below limit " the WS troubleshooting manual say there is a leak in the system. ( not a failed sensor )

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tbh i found this daunting to do so i didn't do it here is what i did tonight. 1) ran the charcoal vent valve command ->no audile click --- bad power and ground? -- i check these before and the continuity + voltage readings where good 2) rechecked the solenoids F and G with a 9v battery -> F good..."new" Pittsburgh brand G was not activating which is very odd..i don't know how this suddenly failed since i installed it. 3) replace the G with the old one that was never broken to begin with 4) ran the "short test" in PIWIS and no longer having p0455 fault code BUTTTT "condition flag" is a not go as the tank pressure difference is 3052mbar which indeed makes me believe the sensor is bad or the connector to it. Anyways i should have a new sensor on Wednesday. The fault memory is empty. 5) performed a negative pressure test from the engine side (via the line to the left of the regeneration valve with port D and E plugged at the front) using my oil extractor kit. It maintained an overall steady negative 12 incH2O. OMG this has been the ****tiest project since i've own the car. Car registration expired since end of June. ugh.

Well new sensor but now it�s negative 4500 mbar. I am tired of this. Time to take it to the expert diagnostician.

replaced: -regeneration valve in engine bay -filler neck breather valve -- wrapped around the filler tube -gas cap -"G" and "F" solenoids passed bench test -new neck collar and rubber seal on top of the fuel tank -new bosch fuel tank pressure sensor -good working used charcoal canister (minimal resistance with blow test) ugh so independent porsche shop couldn't figure it out. still can't pass the PIWIS short test as the tank pressure difference is now 1098mbar with the new bosch sensor. Claude AI said to disconnect the sensor and got 31134mbar and concluded that this proves good power and signal from the DME. Maybe the clone PIWIS and dongle are the problem? I haven't gotten the P0455 for a long while now but can't pass the stupid short test. I may be fatally relaying on PIWIS? Maybe the car is already fix so i should just drive it and get the emission test. it otherwise drives great without any engine codes! i once again ran a smoke test using my old smoker through the fuel filler neck with a manometer in series and with "E" nipple capped but couldn't maintain pressure despite no obvious leak anywhere. However i do recall before seeing smoke somewhere behind the sheet metal closes to where the filler neck attaches to the fuel tank ----- but this only happened once and never observed it again. the one valve i haven't been able to actually bench test is the valve (see pic) that is super hard to get to right next to the fuel tank behind the sheet metal. i've seen one post where they actually had to cut open sheet metal (see pic) in the frunk to get to it instead of dropping the tank. Please help....................

Does the failing of this short test keep the readiness indicators from setting? If readiness is complete, there is no CEL, and there are no codes, go get your smog test. I can’t believe they would run this kind of detailed test. Mine('02 996) has a persistent P1109 code. I’ve had it for years. I’ve looked at many many things to get rid of it. But, readiness completes, there’s no CEL, and this code is not on a list that they can see with a regular ODB2 scanner. Passes smog every time

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thanks for this genius of an idea! As far as I thought the evap system had to be on the ready butttttt I just checked and AI says I still would like to know what the hell is going on with my evap.

Nice. You should take that image with you to the tester. Maybe it's hardcoded in their tester, but you should have this to bring up the discussion if it doesn't. Good luck with the test. The evap sensor seems to be different on everyone's car. My 957 clears all monitors pretty quickly where my 996 needs an overnight cooldown for the evap monitor to clear.

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I just did mine in Utah and got sent home because some of my monitors weren�t ready. I�m not 100% sure if I reset them by having my battery disconnected for so long or if it happens when you clear the DME codes, but you have to do a Porsche specific drive cycle (similar to other cars) to get the monitors ready. I followed the drive cycle in the link below. Took me two cycles to get them all ready, the tank one didn�t set as ready on the first drive cycle for me. Do yourself a favor and check them before you head over to get tested. https://docs.lnengineering.com/artic...fuel-injectors

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thanks for that link!

Emission passed with just evap not ready. Stupid evap ugh. Hopefully the p0455 never shows its ugly head again. Even with the strict driving to get the system ready.

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Did you try the drive cycles? Pretty sure that�s the only way to get it to reset.

Nice. Now you have less stressed time to figure out the evap. Mine is currently stuck in CARB referee hell. I have the Magna-flow replacement cats. Magna-flow had them certified by California for use many years ago. They are on the list of accepted cats and the smog center that I've been going to for 20 years failed it for visual. One of the columns in the table says the car should have 4 cats. And when you look at ours, it only has 2 bodies where the cats are. He didn't know there was a 2 in 1 cat. He wants to see 4 cat bodies. How stupid! To be fair, I didn't know either, but simple searching and AI work easily shows that these are 2 in 1 cats. O2 sensor coming out of the body at the midpoint is the tell. Anyway. Nice work. Looking forward to hearing the rest of the story.

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yea sure did. Never finished but also no p0455.

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well hopefully the story ended today .😂

Well of course I spoke way too soon. P0455 is back. Fun stuff.

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You may want to remove the battery tray and take a look at the fuel pump sensor wiring...I had the same code and tracked it down to wires that had abraded away. Simple solder and shrink wrap repair.

Unfortunately not as simple. I�ve checked the wiring and it�s fine.