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ML320 2002
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Discussion Starter #1
I have the low fuel light flashing together with Check engine light. P0455 Evaporative Emission System (large leak).

Replaced the fuel cap which is reported to be a common cause, but the code returned immediately. What tests or visual inspections I can do before taking it to a Smoke test?
 

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Dallas, Texas
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Hose connections to and from purge valve in engine compartment, hose connection to shut off valve by the spare wheel. P0455 will also get set when fuel tank pressure sensor is stuck.
 

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ML320 2002
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Discussion Starter #3
Thanks Witek. I just checked the hoses around the shutoff valve and the canister. I did not see any sign of deterioration.
 

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2000 E 320 Wagon + 2002 ML 500 SUV
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John:

Is that tube that you had the vacuum leak af part of the fuel tank system (next to tank inlet - it appears) ?

Tube is metal ? How did you resolve it ?

Thank you for sharing details.

I got a P0455 code but fortunately it was gas cap, for now.

David in East Texas
 

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John:

I got a P0455 code but fortunately it was gas cap, for now.

David in East Texas
When everything else checks out....
Gas caps can still get real finicky as these cars age and pull the P0455 code when not closed correctly or even closed correctly but just not right.
Even had to wipe the inside seals clean (although they looked clean) to clear the code. Had to do this on the w202 several times to keep it from popping up.
Ah, to deal with the "finicks" of these vehicles. :)
 

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2000 E 320 Wagon + 2002 ML 500 SUV
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10-4 on finicky gas caps.

I did that to my tired old factory cap finally it didn't help.

Got a new Stant Gas cap from O'reillys and no issues 6 months now, PTL.

I did suspect the Underhood valve & related fuel vacuum hoses, the are original for sure.

Cheers - David in East Texas
 

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1998 ML320
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Just a couple of thoughts to keep in mind - if the gas cap and solenoid valve check out OK, then consider the RUBBER connector that joins the SMALL(plastic?) line from the fuel filter to the LARGER plastic fitting on the upper driver-side of the fuel tank. This piece has been documented to fail a few times. In my case (reported in this link here) the leak was slowly getting worse - so I started with a P0442 code that eventually became a P0445 code. Another description of the same failure (with replacement part number) is here.

Be aware that in the first link above I described using Goop to seal up the leak rather than replace the line. Unfortunately, that repair only lasted a few months. The code returned, and a smoke check revealed a leak at the same place. My son has that car now and he is planning to replace the line in the next week or so.

As noted above, you'll need to remove the left rear wheel and wheel liner to get good access to this line. Good luck. Let us know where the leak turns out to be.

Stephen
 

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Discussion Starter #10
I finally got the smoke test done: NO LEAK detected. The low fuel light flashed again last week. There is a pending P0455 code. What would you do next?
 

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During smoke test shut off valve needs to be closed using component activation. That takes you to the screen that shows current value of pressure sensor. As you apply pressure (smoke) value needs to rise. When you apply vacuum value needs to lower.
 

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Discussion Starter #14
Is DAS/Xentry the only way to test this sensor? I neither have DAS nor a smoke machine. :(
 

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Discussion Starter #16
Scanner with live data display that shows fuel tank pressure? Vacuum pump? Volt meter? Few vacuum plugs and caps?
This is my first CEL after 16 years of ownership. Until now, I did not need a professional scanner.:wink Is it time for a C3 DAS/Xentry? Autel 802?
Vacuum pump=yes, Volt meter=yes, plugs=I can find some.
 

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This is my first CEL after 16 years of ownership. Until now, I did not need a professional scanner.:wink Is it time for a C3 DAS/Xentry? Autel 802?
Vacuum pump=yes, Volt meter=yes, plugs=I can find some.
Lucky you.:smile

STAR TekInfo

Run tests 30.0, 31.0, 33.0, 33.1. Where is says charcoal canister shut-off valve Y58/4 activated you cap it or plug vent hose.
 

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Just to clarify those test. You will be checking voltage supply (33.1) at pins 4d-6d 5V and pressure signal (33.0) at pins 4d-5d Check can be done at ECM or pressure sensor.

White-Pink voltage supply. White-Gray signal.
 

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Discussion Starter #19 (Edited)
Just to clarify those test. You will be checking voltage supply (33.1) at pins 4d-6d 5V and pressure signal (33.0) at pins 4d-5d Check can be done at ECM or pressure sensor.

White-Pink voltage supply. White-Gray signal.
I have not done the vacuum tests yet. Need a connector to fit the fuel line plugging to the purge valve. I will look for perfectly fitting fuel line connectors at auto part stores this weekend. It looks line fuel lines are 3/8".

PS. I have not seen flashing low fuel light in a week. Hopefully the new fuel cap gasket is now fitted in place.
 

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Discussion Starter #20
I plugged the canister hose. I connected my brake bleeder to the fuel line normally connects to the purge valve. Unfortunately, the handheld brake bleeder is not creating a vacuum :frown. Do I need a more powerful vacuum?
 
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