P0446 code - Charcoal canister shut-off valve - Mercedes-Benz Forum

LinkBack Thread Tools Display Modes
post #1 of 3 (permalink) Old 03-23-2010, 08:15 PM Thread Starter
BenzWorld Newbie
Date registered: May 2009
Posts: 4
Mentioned: 0 Post(s)
Quoted: 0 Post(s)
(Thread Starter)
P0446 code - Charcoal canister shut-off valve

Hello All,

my wifes 02 ML320 is showing an 0446 code. If I clear it using my scanner the code will reappear right away (2 starts cycles). Performance of the car does not seem to be affected in any way. I have replaced the actual canister shut-off valve itself with no change, and had the vehicle smoke tested which proved there where no system leaks. However it appears that neither the shut-off valve nor the purge valve under the hood seems to be engaging. Both are getting 14-volts on their power wires when measured to chassis ground, and do engage if "chassis" ground is applied to the low side. However I only measure ~10volts between the power wire and its own ground signal wire. Not enough to trigger them I'm guessing. I understand that the ground wire carries the control signal from another module (N3/10???) which I am not sure where is located.

Soooooo, long story short, I hoping for any clues or direction to help solve this mystery. Am I overlooking something obvious? Where might I find this N3/10 module? Other likely culprits? Thanks to all.

skymaster is offline  
Sponsored Links
post #2 of 3 (permalink) Old 05-25-2010, 11:46 AM
BenzWorld Newbie
Date registered: Apr 2010
Vehicle: 2001 E320 sedan
Location: Illinois
Posts: 1
Mentioned: 0 Post(s)
Quoted: 0 Post(s)
New charcoal canister shut-off valve not closing.

2001 E320 appears to have these same symptoms. Installed a new charcoal canister shut-off valve which is not closing. Voltage measured at the valve measures the expected +12v when system calls for the valve to close. Bench testing proves the valve is working. The line current appears to be too low to close the valve. Any ideas? Expecting a dirty connection but unsure as to were to look for the problem.

This is my first posting and looking forward to hearing from those with experience. Thank you for the support, Dennis
Bohmer is offline  
post #3 of 3 (permalink) Old 05-27-2010, 08:16 AM Thread Starter
BenzWorld Newbie
Date registered: May 2009
Posts: 4
Mentioned: 0 Post(s)
Quoted: 0 Post(s)
(Thread Starter)
Hi Bohmer,

After several hours in the local MB shop we did finally trace down the problem. It seems that both the Charcoal filter valve and the purge valve (located under the hood) have 12v applied all of the time and the main controller switches the ground to open and close them. In my case the wiring harness had chaffed in a small spot where it runs through the left rear wheel well in into the body. This allowed moisture into the ground wire and caused it to corrode and fail. Because I was using chassis ground when taking my measurements I didn't catch this. So the fix was to replace about 6 inches of the wire to remove the bad section just where it enters the body of the car. 4 hours of labor for a few cents of wire. Frustrating but it's fixed and working as it should now.

Hope this helps

skymaster is offline  
Sponsored Links

  Mercedes-Benz Forum > General Mercedes-Benz Forums > General Mercedes-Benz

Quick Reply

Register Now

In order to be able to post messages on the Mercedes-Benz Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:


  • Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
    Thread Tools
    Show Printable Version Show Printable Version
    Email this Page Email this Page
    Display Modes
    Linear Mode Linear Mode

    Similar Threads
    Topic Author Forum Replies Last Post
    DIY Charcoal Canister & Valve CambridgeMA W210 E-Class 7 08-09-2011 01:13 PM
    gas leak from charcoal canister shutoff valve dabek10 General Mercedes-Benz 7 03-28-2009 01:51 PM
    Code P0455 & Charcoal Canister & Valve WhiteGrace W202 C-Class 2 09-22-2008 08:55 PM
    Charcoal canister shut-off valve? Dan Tomlinson R129 SL-Class 2 03-29-2008 02:04 PM
    1997 S420 Charcoal canister and valve location aljabari W140 S-Class 0 09-14-2007 06:39 PM

    Posting Rules  
    You may post new threads
    You may post replies
    You may not post attachments
    You may not edit your posts

    BB code is On
    Smilies are On
    [IMG] code is On
    HTML code is Off
    Trackbacks are On
    Pingbacks are On
    Refbacks are On


    Title goes here

    video goes here
    description goes here. Read Full Story
    For the best viewing experience please update your browser to Google Chrome