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greetings,

i've got a code P0455 (EVAP emissions control system leak LARGE) - does anyone know how to resolve this problem? my car is a '99 cab 996.

thanks

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P0455 Fuel Tank Ventilation System (Major Leak) - Below Lower Limit

Potential causes:

- Tank cap missing or o-ring bad or missing.

- Ventilation lines detached from EVAP canister.

- Ventilation line detached from tank.

- Ventilation lines detached from operating vent valve.

- Ventilation line detached from fuel tank vent valve.

- Break in ventilation lines.

post-2-1152725654_thumb.jpg

1 - EVAP canister purge valve

2 - EVAP canister

3 - Purge air

4 - Tank

5 - Pressure sensor

6 - Shutoff valve

7 - Operating purge valve

8 - To intake manifold

9 - Vacuum control valve

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wow, thanks that was fast. i've noticed before the code that the tank wasn't filling up all the way when i gassed her up. i've also noticed there isn't any pressure released when i remove the gas cap. do you think its my purge valve? thanks again for such a detailed illustration of the fuel system...i'm sure i'll be able to nail down the fix.

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i replaced the gas cap and cleaned the o-ring really well with silicone. i also bought one of those pocket scanners for piece of mind next time. i erased the code and haven't seen it come back yet after a couple of days. if it comes on again i'll start looking for purge valves and disconnected ventilation hoses...thanks for the help.

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The P0455 CEL code comes on once every tank of gas or so I clear it with my OBDII.

When the gas cap is removed (new cap) you can hear the air sucking into the filler opening for ~10 seconds.

I have pulled the inner fender and inspected the canister and there was nothing obviously disconnected or cracked.

Leads me to believe that there is not a large leak in the system.

If there was a large leak the inside tank and outside pressure should be the same.

On Loren's drawing of the evap system there is a pressure sensor #5 that looks like the sensor that would cause the P0455.

I inspected the sensor on top of the gas tank and it was connected and didnt look to be damaged.

It looks like the only sensor in the system so I was thinking about replacing it.

Is there a test I can perform on the sensor to see if its bad before I buy a new one?

Any tips on the replacement?

Thanks

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Hey guys. I had the same CEL , I looked at the gas cap cause I can clearly see the cracks on the rubber ring of the cap. Now I got new caps and still coming back. When I open the cap to fill the gas there is no sucking sound. I guess there is a large leak based on what I've seen. Any suggestion on where to start? Any suggestion is appreciated. Thanks in advance guys.

-Han

Edited by hph996

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Mine has the same code. It comes back about once a month. I replaced the gas cap last time. Code is back. I cleared it with a code reader. I guess it is time to start checking lines and the canister.

Edited by carsareart

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Mine has the same code. It comes back about once a month. I replaced the gas cap last time. Code is back. I cleared it with a code reader. I guess it is time to start checking lines and the canister.

Any updates to this Problem?....would greatly appreciate it....having the same issue.....get the cel (p0455) about once per tank.....when I remove the gas cap, no sound.....no pressure. I replaced the cap, inspected the canister behind the wheel well, removed some of the fittings, cleaned, reinstalled.

Thanks in advance!

2000 Boxster 2.7

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Did anyone get a solution to this? I have similar errors in my 07 Cayman S:

 

 

Bosch Digital Motor Electronics Motronic 7.8.1

 

Current Fault Codes

 

P0455:
Tank system - major leak

 

P0456:
Tank system - fine leak

 

 

 

Porsche Access System - PAS

 

Current Fault Codes

 

8004:
Terminal 50

Edited by SpawnyWhippet

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Seems like my CEL came on with codes P0445 and P0446 due to the cracks in the fuel cap seal (see arrow in pic). Amazing that such a tiny problem causes the CEL to come on. Fingers crossed that there is nothing else to fix. This was a $20 repair so far...

 

FuelCapcracks.jpg

  • Upvote 1

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P0455

Leakage in fuel tank system

Diagnostic conditions

D Vehicle speed = 0 km/h

D Engine speed = 0 rpm

D Correction factor, height > 0.73

D Coolant temperature upon starting the engine may be no more than 6.8 K above ambient temperature

D Coolant temperature when engine starts > 3.8 °C

D Period for which the engine needs to have been running before ignition is switched off > 20 minutes

D Ignition has been switched off for at least 10 seconds.

D Ambient temperature 4 … 35.3 °C

D Active charcoal filter load < 3 for minor leak

D Fuel tank fuel level 10 … 54 litres

D Battery positive voltage 11.02 ... 14.5 V

D No fuel tank filling

D No faults detected for ambient pressure sensor, coolant temperature sensor, vehicle speed sensor

D No output stage faults detected for DMTL pump motor, DMTL switch-over valves and tank vent

D No fault detected for tank vent (flow)

E The diagnostic conditions can also be established using the PIWIS Tester via the short test "tank leakage test". After the test has begun, the ignition must be switched off.

F NOTE

E In this context, please also observe the function description.

Possible fault causes

E Tank cap not closed correctly, leaking or missing

E Purge air line leaking

E Tank vent leaking

E DMTL (Tank Leakage Diagnostics Module) leaking

E Leakage in fuel tank system

Page 140 of 398 07/20/2006

Function description

Tank leakage test/DMTL – Tank Leakage Diagnostics Module

F Note

E The tank leakage test is performed only on USA vehicles.

Construction of the tank leakage diagnostics module:

The diagnostics module consists of an electric motor with a small air pump, switch-over valves and a reference nozzle.

In addition, the modul is heated so as to prevent the forming of condensation and ice.

Procedure of the function:

E The pump is operated via an electric motor and conveys air through the reference leak. The power consumed during this process is determined.

E The switch-over valve switches and the air current is now directed into the fuel tank. The power consumed during this process is also determined. After a waiting period dependent on the fuel tank fuel level, it must be at least as high as the power consumption was during the reference leak test if the tank system is leak-free.

E The system is identified to by leaking if the power consumption is lower during the actual leakage test as it was during the reference leak test.

E An evaluation of the power consumption levels when the pump is started and after the switch-over valve has switched serves to identify faults within the tank leakage diagnostic module (e.g. pump blocked, motor spins at idle speed, valve does not switch etc.).

E The diagnosis of heating, motor and switch-over valve is performed via the output stage of the DME control module.

 

 

 

P0456

Leakage in fuel tank system

Diagnostic conditions

D Vehicle speed = 0 km/h

D Engine speed = 0 rpm

D Correction factor, height > 0.73

D Coolant temperature upon starting the engine may be no more than 6.8 K above ambient temperature

D Coolant temperature when engine starts > 3.8 °C

D Period for which the engine needs to have been running before ignition is switched off > 20 minutes

D Ignition has been switched off for at least 10 seconds.

D Ambient temperature 4 … 35.3 °C

D Active charcoal filter load < 3 for minor leak

D Fuel tank fuel level 10 … 54 litres

D Battery positive voltage 11.02 ... 14.5 V

D No fuel tank filling

D No faults detected for ambient pressure sensor, coolant temperature sensor, vehicle speed sensor

D No output stage faults detected for DMTL pump motor, DMTL switch-over valves and tank vent

D No fault detected for tank vent (flow)

E The diagnostic conditions can also be established using the PIWIS Tester via the short test "tank leakage test". After the test has begun, the ignition must be switched off.

F NOTE

E In this context, please also observe the function description.

Possible fault causes

E Tank cap not closed correctly, leaking or missing

E Purge air line leaking

E Tank vent leaking

E DMTL (Tank Leakage Diagnostics Module) leaking

E Leakage in fuel tank system

 

Function description

Tank leakage test/DMTL – Tank Leakage Diagnostics Module

F Note

E The tank leakage test is performed only on USA vehicles.

Construction of the tank leakage diagnostics module:

The diagnostics module consists of an electric motor with a small air pump, switch-over valves and a reference nozzle.

In addition, the modul is heated so as to prevent the forming of condensation and ice.

Procedure of the function:

E The pump is operated via an electric motor and conveys air through the reference leak. The power consumed during this process is determined.

E The switch-over valve switches and the air current is now directed into the fuel tank. The power consumed during this process is also determined. After a waiting period dependent on the fuel tank fuel level, it must be at least as high as the power consumption was during the reference leak test if the tank system is leak-free.

E The system is identified to by leaking if the power consumption is lower during the actual leakage test as it was during the reference leak test.

E An evaluation of the power consumption levels when the pump is started and after the switch-over valve has switched serves to identify faults within the tank leakage diagnostic module (e.g. pump blocked, motor spins at idle speed, valve does not switch etc.).

E The diagnosis of heating, motor and switch-over valve is performed via the output stage of the DME control module.

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18 hours ago, SpawnyWhippet said:

Seems like my CEL came on with codes P0445 and P0446 due to the cracks in the fuel cap seal (see arrow in pic). Amazing that such a tiny problem causes the CEL to come on. Fingers crossed that there is nothing else to fix. This was a $20 repair so far...

 

FuelCapcracks.jpg

 

Without a doubt the most common cause of this fault. Nice work!

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I have 1999 996 with a CEL and a P0455 DTC.....car runs great, right now, but is smelling of gas.  I can reset the code, but it comes back.  I recently changed the fuel cap and vent bledeer valve and can fill car up now and runs smoother and faster. Any thoughts?

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29 minutes ago, 1999911 said:

I have 1999 996 with a CEL and a P0455 DTC.....car runs great, right now, but is smelling of gas.  I can reset the code, but it comes back.  I recently changed the fuel cap and vent bledeer valve and can fill car up now and runs smoother and faster. Any thoughts?

 

Check the vent lines under the fender for damage or leaks.

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Hi, I got the error P0455. I was able to put in gas, but only if I held the pump at a certain angle. Thinking it was the Fuel Tank Vent Valve that was the problem, I replace my Fuel Tank Vent Valve, but now I can't even put any gas in the car at all. Do anyone else have any tips or solutions? I would like to get to the root and diagnose my problem. 

Porsche Boxster 2002 

537.jpeg

Edited by JohnPorsche

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Hey man, I just dealt with this code, my culprit was the vent valve line on the fuel pump, under the battery compartment. Mine had completely broken off, your's could be clogged or pinched. I found my problem by unplugging the line at the regeneration valve in the throttle body and blowing some compressed air into it.

Edited by 01slvr996

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Hi, I got the error P0455. I was able to put in gas, but only if I held the pump at a certain angle. Thinking it was the Fuel Tank Vent Valve that was the problem, I replace my Fuel Tank Vent Valve, but now I can't even put any gas in the car at all. Do anyone else have any tips or solutions? I would like to get to the root and diagnose my problem. 

Porsche Boxster 2002 
537.thumb.jpeg.0c4cd3d9b0f7629dcdb89d8bc7ced40f.jpeg

I replaced the tank vent valve on my '02 Boxter S with similar symptoms. Had the same issue. I found a small cylinder with an electronic lead on it. I discovered (hours of research and install/reinstall of the valve) that this thing is a magnetic sensor that fits in a slot on the tank vent valve. When you look, it will be obvious. The sensor pops off when you remove the valve. Don't slap your head too hard!


Sent from my iPhone using Tapatalk

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Mine has started throwing the code again, last time all I had to do was replace the gas cap, and keep it tight. 

Here we go again. It lasted almost 10 years with the last fix. 

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lots of information about this on the search engine.  the search engine is a good friend.

check this out and good luck:  

 

 

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On 2/10/2017 at 1:51 PM, Slainte336 said:


I replaced the tank vent valve on my '02 Boxter S with similar symptoms. Had the same issue. I found a small cylinder with an electronic lead on it. I discovered (hours of research and install/reinstall of the valve) that this thing is a magnetic sensor that fits in a slot on the tank vent valve. When you look, it will be obvious. The sensor pops off when you remove the valve. Don't slap your head too hard!


Sent from my iPhone using Tapatalk

 

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Are you referring to the vent valve that sits on top of the fuel tank with the three wire connector? It is the only one I see there. Thanks

 

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Soooo.... I have the same CEL P0455  however my check engine light does not come on until I really get on the car and drive it hard running the tac about 5000 RPM and above. As soon as I stop driving the car hard the light comes on in about two or three seconds.  Driving the car around town shifting between 3000 to 3500 rpm does not yield a CEL. The gas cap seal looks fine but I ordered one just in case.....Ideas?

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