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2003 ML350
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Discussion Starter #1
Hi everyone,
I have a Check Engine Light on, went to Autozone today and they told me it was a P0446. After searching on this site, it all point to the charcoal canister shut off valve. Went to check it under the car and seem like a simple DIY. Now my question is, will the light turn off once its replace or will I have to get it reset? Also, its pretty expensive at mercedes benz. Just called and its $231 plus tax. Does anyone know any website that sells this part for cheaper? Mercedes benz part store seems to rip you off on everything. Any inputs would help. Thanks
 

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2003 ML350
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Discussion Starter #3
Thanks for the reply. Car is 2003 ML350. What category is this part under? I cant seem to find it anywhere on the website.
 

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2003 ML350
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Discussion Starter #5
UPDATE: I took apart the canister valve and cleaned it. Put it back on and made sure the wiring was securely plugged in. Reset the battery and the Check Engine Light turned OFF. Been only driving around for 15 miles, hopefully it stays off:bowdown:
 

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04 CLK500 Cabriolet(sold), 02 ML500(current), 03 E500(current), 2015 GL550 Designo(current)
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UPDATE: I took apart the canister valve and cleaned it. Put it back on and made sure the wiring was securely plugged in. Reset the battery and the Check Engine Light turned OFF. Been only driving around for 15 miles, hopefully it stays off:bowdown:
Hey kevinbui86,
I am having the same issue with my 02 ML500, I scanned it and got a P0455: Gross Vapor Leak. So far I only replaced the Fuel Filler Cap and cleaned the Purge Valve more than once(with MAF cleaner) but the CEL keeps coming back on after the fuel reserve light flashes first...

My next step will be, changing the Purge Valve since I cant seem to hear it ticking at all... but my main concern is the following,, almost every time i refuel the car the nozzle stops way before my tank is full, sometimes right when I start refueling.. so I was told that this is caused by a bad Charcoal Canister Shut off Valve which runs about $218 from MB.. So did the Shut off valve cleaning end up resolving your issue permanently?? Can you please provide some instructions or a reference to reach the shut off valve and clean it??

Thanks in advance for your help!
Moe
 

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02 ML320 06 ML500
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My next step will be, changing the Purge Valve since I cant seem to hear it ticking at all...
Before you change the Purge Control Valve, turn the key to the #2 position and with a test light see that voltage is present at the blue wire. If so, then run a small wire from a known good ground to the Orange wire on the connector and simulate pulse width modulation by tapping the jumper wire to the Orange wire multiple times. Every time you make contact the valve should click.

If everything is in order make sure all the prerequisites are in place and babysit the Purge Valve and wait for activation.
 

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04 CLK500 Cabriolet(sold), 02 ML500(current), 03 E500(current), 2015 GL550 Designo(current)
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Thank you very much for the help 43sqd. I followed your instructions, made sure there was power at the blue wire but noticed no clicks what so ever when making ground contact with the orange wire, tried it with diff grounds and wires, does that mean the valve is not functioning?? and if it is not functioning, could it result in the Charcoal Canister shut off valve to be stuck in one position causing the gas nozzle to keep clicking off even with a near empty tank or is that unrelated to it??
 

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moe, if the test was done properly and the valve does not click, then it is toast. The valve sells for $60-65 at the dealer.

As for the gas nozzle clicking off prematurely, that is a separate issue altogether and has no bearing on whether or not the Purge Valve operates. Check to see that the round flap is still in place at the filler neck (#47)
 

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Update:
Purchased the Purge Valve and replaced it, I didn't wipe out the fault code to see if the CEL goes away on its own but instead I got the flashing low fuel indicator again :( I am yet to test it in case it is faulty though..

The premature clicking of the nozzle is actually not an every time thing, I noticed it happens probably once every 5-6 fill ups maybe less frequent..

So, where should I focus my attention at this point, I am leaning towards either the Shut off valve and/or the Fuel tank pressure sensor, the prob is each of these parts is close to $200 each from MB and I am torn whether I should I just send it in for a test perhaps they can tell me which of the two is bad unless its a whole different issue. Anyone know what such tests they can do to the actual sensors/valves involved other than the initial computer scan?? and how long will such diagnosis take??

Thanks again for your very much appreciated information 43sqd! Cheers!
 

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As for the fuel round flap it is there but i noticed it stays a little bit open, it does seem to return to its orig position but does not fully shut the filler neck, it remains hanging a bit lower about 1/5th of an inch..
 

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Update:
Purchased the Purge Valve and replaced it, I didn't wipe out the fault code to see if the CEL goes away on its own but instead I got the flashing low fuel indicator again :( I am yet to test it in case it is faulty though..

The premature clicking of the nozzle is actually not an every time thing, I noticed it happens probably once every 5-6 fill ups maybe less frequent..

So, where should I focus my attention at this point, I am leaning towards either the Shut off valve and/or the Fuel tank pressure sensor, the prob is each of these parts is close to $200 each from MB and I am torn whether I should I just send it in for a test perhaps they can tell me which of the two is bad unless its a whole different issue. Anyone know what such tests they can do to the actual sensors/valves involved other than the initial computer scan?? and how long will such diagnosis take??

Thanks again for your very much appreciated information 43sqd! Cheers!

Moe, first things first, clear the codes and see whether the new Purge Valve is working or not.

For the time being don't be overly concerned with the nozzle clicking off every 5-6 times you fill up.
 

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That is not the issue. Have you had the fuel cap pressure tested?
I only replaced the fuel cap but I have not done any pressure tests on it due to lack of tools to do so myself, any such affordable tools out there worth keeping around?

Moe, first things first, clear the codes and see whether the new Purge Valve is working or not.

For the time being don't be overly concerned with the nozzle clicking off every 5-6 times you fill up.
I was going to reset it but I thought/read on some forum if the PV was the only cause then the system will eventually learn that it has been fixed and hence remove the CEL automatically, am I wrong here? I will erase it today anyway and hope it never comes back, it took about 2 weeks last time I erased the code for it to come back..

And its certainly not the nozzle clicking off once in a while it's that huge bright orange CEL staring at me all the time its annoying :) and maybe because the ML is mainly used by my wife driving with the kids and I really do not want any breakdowns on the road esp if I was not there with her.. Should I expect any?
 

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Is the newly installed Purge Valve working............yes or no.
my bad 43sqd, forgot to mention the main point.. I did test the PV and it pulsed as I grounded it but.... I didn't get the pulsing while it's connected normally on a cold start but maybe I didn't babysit it long enough.. So I reset the CEL anyway to see if it comes back however the other thing I want to mention is.. I noticed the part number on the new PV is actually different from my orig one, the new one is A 212 470 27 93 28 so I called the MB dealership and they said it's an interchangeable part that works on more than one MB model.. can someone confirm this for me please as my orig PV part num starts with A 163 ?????

I will have more time to babysit the new PV this evening to see if it pulses on its own and will report back..
 

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99 ML430, 00 ML320, 05 E500 4matic Wagon
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A 212 470 27 93 28 is the current part listed for the application. List is $75 discount is
between $54-$65.
 

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my bad 43sqd, forgot to mention the main point.. I did test the PV and it pulsed as I grounded it but.... I didn't get the pulsing while it's connected normally on a cold start but maybe I didn't babysit it long enough.. So I reset the CEL anyway to see if it comes back however the other thing I want to mention is.. I noticed the part number on the new PV is actually different from my orig one, the new one is A 212 470 27 93 28 so I called the MB dealership and they said it's an interchangeable part that works on more than one MB model.. can someone confirm this for me please as my orig PV part num starts with A 163 ?????

I will have more time to babysit the new PV this evening to see if it pulses on its own and will report back..

Make sure that the fuel level is no less than 1/4 and no more that 3/4 for the evaporative monitor to set properly (see para. 7)
 

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Thank you for the instructions 43sqd and for your info Noodles

UPDATE:
So I finally got to feel that consistent ticking in the PV during normal operation..so that rules out a PV malfunction I guess.. and while driving to work this morning the low fuel light started flashing again and the CEL came back on shortly after.. it normally took one to two weeks to come back before but this time it only took 3 days..

So is time for a pressure test? or is there something else I can check or clean or replace before sending it in for tests?
 

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Thank you for the instructions 43sqd and for your info Noodles

UPDATE:
So I finally got to feel that consistent ticking in the PV during normal operation..so that rules out a PV malfunction I guess.. and while driving to work this morning the low fuel light started flashing again and the CEL came back on shortly after.. it normally took one to two weeks to come back before but this time it only took 3 days..

So is time for a pressure test? or is there something else I can check or clean or replace before sending it in for tests?
Since you have already replaced the fuel cap and the Purge Valve, it is now time to find an independent mechanic or take it to the dealer and have the evaporative system put through a smoke test.

Or you can run these tests, but that would require and lift and disconnecting hoses and the like.
 

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