bobinyelm

2002 C320 Wagon 70k miles

I sometimes get a P0446 DTC immediately when I start my car.

If I erase the code, I may go another several hundred miles w/o getting the Check Engine Light again, at which point the CEL will illuminate right at engine start.

I understand this may be the Evaporative Charcoal Canister Shutoff Valve.

1) Do you guys confirm this?
2) If so, where is the canister located on my vehicle?

I have a CD manual on order, but I am due for State emissions inspection and need to get it re-licensed ASAP so cannot wait for the manual, which I hope will show the location and depict the valve.

Thanks,
Bob

Glyn M Ruck

P0446 = Evaporative Emission Control System Vent Control
Circuit Malfunction







Check all pipework in diagram 2 for leakage - smoke test is best. Check fuel cap. A common cause of EECS problems is a cracked fuel filler pipe.

Check purge valve in the engine compartment. See red circle in pic.

Good luck!

bobinyelm

So the P0446 doesn't coincide with any particular portion of the evaporative system, and it could be either valve, the filler neck, or the cap?

Is there a way to see the photos? (They are little boxes with "Xs" in them).

I was at my MB dealer today trying to buy a new key, and they said they replace BOTH valves with any evap MIL, which is about $1200, which is beyond my means, though I can go for the valves themselves ($480 plus tax), but would rather track it down to ONE, or maybe just a hose.

If it's a hose or cap, it seems it should give a MIL after so many miles, or on every cycle, but sometimes I can go a LONG time between MILs. A leaking hose (as opposed to a sticking valve) seems like it should be leaking consistently?

Just trying to narrow the problem down a bit...

Thanks for the photos-nice to know he purge valve is under the hood. The dealer said the canister and shut-off is inside the RR fender (remove the wheel and the fender liner). I assume they are correct? They said the shut-off valve attaches directly to the charcoal canister itself. They said they replace a lot of canisters, even if they don't leak. How does one know if they are bad if they are air-tight?

Today I swapped the fuel cap w/ the one on my '03 SLK (which doesn't throw a code) to see if the DTC stops recurring. Unfortunately I don't have a smoke generator at my disposal.

Thanks,
Bob

Glyn M Ruck

You have to be signed in/logged on to see the pictures. If you have clicked on the e mail link to enter the forum & can't see them then enter the forum via mbworld.org & this will usually fix the problem. The pictures are there - I can see all 3 of them just fine.

Experience with the damn EECS tells me that these codes can mean a number of things even though there are specific codes for individual items. As this is a circuit code check the electrical connectors to the valves first for corrosion etc.

The rear unit is indeed under the rear fender shroud.

Many canisters get replaced unecessarily - unless they leak they are seldom the problem.

Also - be carefull not to overfill the car with Gas - You can saturate the canister & generate an EECS CEL.

If you have no test gear then the best you can do to eliminate items is to swap them out with the same part from your SLK & see what fixes the problem. I fully understand not wanting to replace things that are not broken. I'm the same but on modern cars the dealer has the benefit of test gear & being able to try things from the parts dept. or just replace them all & sting the owner of the vehicle.

The front purge valve is usually easy to check as they click quite loudly. Put a screwdriver to your ear and touch the valve & listen for clicking. Or use a $10 engine stethoscope.

Your logic is correct on pipe leaks but the OBDII system counts number of same errors before reaching a threshold & triggering a CEL.

bobinyelm

Thank-you for your hints, and yes, the pictures magically "appeared" on my second viewing.

Good point about the requirement of multiple faults before the MIL is triggered. I guess checking for pending codes daily might be a tip off for that as long as I do it often, and before before the MIL illuminates. I can probably get car through inspection between the time the "readiness tests" have been completed with enough drive cycles, and before a pending code trips the MIL once I break the code of how many cycles it takes before a pending code matures into a real one. My temporary plates have an early drop-dead date.

Yes, the dealer has the advantage of being able to replace multiple parts at once as most Benz customers are less price sensitive than people like myself who are content to drive older models worth a fraction of newer models. I've owned 9 MBs since my first, a '59 180, and they were all (except for my Sprinter van, which I bought new) several years old when acquired, even when $4500 would have bought a new 240D in the mid 1970s, so I have never been a "target audience" for Daimler Benz when setting repair costs.

As we walked through the VERY luxurious dealership here in Dallas yesterday, we noted more than 8 vehicles on the showroom with sticker prices above $200,000, and only about 1/2 of the total number of cars (22 on the showroom floor) were below $100,000, and most of those were SLKs with average sticker prices of $65,000-$75,000.

Even when these vehicles are "seasoned" and off-warranty, it doubt a $1200 repair bill for multiple part replacements would cause as much as an eye-blink from the customer, while it lessens the chance of a "come-back" for the service department.

Thanks-
Bob

taylordr61

Glyn,

Would you also have the page the provides the descriptions of the numbers you provided in post #2 above? That would be helpful as I am trying to disgnose a similar P0446 issue with a corresponding Gas smell when we fill the tank.

Don Taylor

Glyn M Ruck

10 A 168 471 06 79 .SEALING RING
FILLER CAP Code: 494/835/921
001
10 A 203 470 13 01 FUEL TANK
Replaced_By: A 203 470 51 01 [006]
001
10 A 203 470 51 01 FUEL TANK
Replaced_By: A 203 470 92 01 [006]
NB
10 A 203 470 92 01 FUEL TANK [006]
001
10 A 203 470 13 01 FUEL TANK
Replaced_By: A 203 470 51 01 [006]
Code: 494
001
10 A 203 470 51 01 FUEL TANK
Replaced_By: A 203 470 92 01 [006]
Code: 494
NB
10 A 203 470 92 01 FUEL TANK [006]
Code: 494
001
10 A 203 470 51 01 FUEL TANK
Replaced_By: A 203 470 92 01 [006]
Code: 494+929
NB
10 A 203 470 92 01 FUEL TANK [006]
Code: 494+929
001
20 A 203 470 00 40 FRICTION RING COMPRESSORS
TANK ATTACHMENT 002
30 A 000 990 39 50 NUT
TANK ATTACHMENT
M18X1.5 002
40 N 000000 0003278 HEX NUT
TANK ATTACHMENT 002
45 A 108 990 03 40 WASHER 002
50 A 203 470 14 20 FILLER NECK
FUEL TANK Code: -494
001
50 A 203 470 14 20 FILLER NECK
FUEL TANK 001
50 A 203 470 17 20 FILLER NECK
FUEL TANK
Replaced_By: A 203 470 19 20 Code: 494
001
50 A 203 470 19 20 FILLER NECK Code: 494
001
50 A 203 470 18 20 FILLER NECK
FUEL TANK Code: 498
001
50 A 203 470 18 20 FILLER NECK
FUEL TANK Code: 918
001
50 A 203 470 19 20 FILLER NECK
FUEL TANK Code: 494+929
001
51 A 203 476 31 26 .HOSE
FROM FILLER NECK TO FUEL TANK 001
51 A 203 476 98 26 .HOSE
FROM FILLER NECK TO FUEL TANK Code: 494/921/835
001
52 A 006 997 06 90 .CLIP
MOLDED HOSE
45-55 MM 002
53 A 230 476 87 26 .HOSE
TANK FOR SERVICE VENTING
1600 MM [404], [409]
Code: 494
NB
53 A 140 476 53 26 .HOSE
FROM RESERVOIR TO VENT LINE FROM TANK
290 MM Code: 494
001
53 A 230 476 87 26 .HOSE
TANK FOR SERVICE VENTING
1600 MM [404]
Code: 494
NB
53 N 916030 0000527 .HOSE
TANK FOR SERVICE VENTING
7.5X3 [404]
NB
54 A 006 997 18 90 .CLIP
CONNECTING HOSE
13-14.5 003
54 A 006 997 18 90 .CLIP
HOSE FASTENING
13-14.5 Code: 494
002
54 A 006 997 18 90 .CLIP
TO FUEL TANK
13-14.5 001
55 A 000 476 92 26 .HOSE
TANK BREATHING
28X4MM [404]
001
55 A 203 476 57 26 .HOSE
TANK BREATHING Code: 494
001
56 A 006 997 29 90 .HOSE CLAMP
HOSE FASTENING
27.5 MM - 28.8 MM 002
56 A 005 997 86 90 .LOOM TIE
LINE MOUNTING
26.5 MM Code: 494
001
57 A 114 997 18 82 .HOSE
FILLER NECK TO CHARCOAL FILTER
13.3X3 MM
Replaced_By: N 916030 0000527 [404]
NB
57 N 916030 0000527 .HOSE
FILLER NECK TO CHARCOAL FILTER
7.5X3 [404]
NB
57 A 203 476 61 26 .HOSE
FILLER NECK TO CHARCOAL FILTER Code: 494
001
58 A 006 997 18 90 .CLIP
HOSE FASTENING
13-14.5 001
59 A 000 995 66 65 CLAMP
FUEL COMPENSATING LINE
11MM Code: 272+494
001
59 A 000 995 66 65 CLAMP
FUEL COMPENSATING LINE
11MM Code: 494
001
60 A 000 476 04 36 CLAMP
REGENERATION LINE
11 MM Code: 494
001
64 A 000 990 03 11 SCREW
M6X18 003
65 A 001 990 12 36 SCREW
FILLER NECK TO SIDE PANEL 001
70 A 140 988 00 25 TREENAIL
FILLER NECK TO SIDE PANEL 001
80 A 203 997 14 81 GROMMET
TANK FILLER NECK Code: 921
001
90 A 168 470 01 05 TANK LOCK
TANK FILLER NECK [009]
001
90 A 230 470 03 05 TANK LOCK
TANK FILLER NECK [010], [409]
001
90 A 168 470 02 05 TANK LOCK
TANK FILLER NECK [011]
Code: -803+494
001
90 A 230 470 04 05 TANK LOCK
TANK FILLER NECK [012], [409]
Code: 494
001
100 A 168 471 04 79 .SEALING RING
FILLER CAP 001
105 A 001 990 23 92 SPREADER RIVET
FILLER CAP
5.2 MM 001
110 A 203 470 28 94 DELIVERY UNIT
WITH FLUID LEVEL SENSOR
Replaced_By: A 203 470 35 94
+001 A 203 470 29 41 [014]
001
110 A 203 470 35 94 DELIVERY UNIT
WITH FLUID LEVEL SENSOR
GOLD [015], [408]
001
110 A 203 470 23 94 DELIVERY UNIT
WITH FLUID LEVEL SENSOR [008]
001
110 A 203 470 22 94 DELIVERY UNIT
WITH FLUID LEVEL SENSOR
Replaced_By: A 203 470 23 94 [008], [016]
001
110 A 203 470 10 94 DELIVERY UNIT
WITH FLUID LEVEL SENSOR Code: 494+929
001
120 A 203 470 25 41 MOUNTING PLATE
WITH FLUID LEVEL SENSOR
Replaced_By: A 203 470 29 41
+001 A 203 470 35 94 Code: -494
001
120 A 203 470 29 41 MOUNTING PLATE
WITH FLUID LEVEL SENSOR
GOLD/ECE [007], [408]
Code: -494
001
120 A 203 470 16 41 MOUNTING PLATE
WITH FLUID LEVEL SENSOR
MAPPS/ECE [008], [013]
001
120 A 203 470 05 41 MOUNTING PLATE
Replaced_By: A 203 470 47 94 [020], [021]
Code: 494+929
001
120 A 203 470 47 94 DELIVERY UNIT
Replaced_By: A 203 470 05 41 [013]
Code: 494+929
001
120 A 203 470 05 41 MOUNTING PLATE [013]
Code: 494+929
001
120 A 203 470 17 41 MOUNTING PLATE
WITH FLUID LEVEL SENSOR
MAPPS/USA [008], [013]
Code: 494
001
120 A 203 470 27 41 MOUNTING PLATE
WITH FLUID LEVEL SENSOR
Replaced_By: A 203 470 30 41
+001 A 203 470 35 94 [013]
Code: 494
001
120 A 203 470 30 41 MOUNTING PLATE
WITH FLUID LEVEL SENSOR
GOLD/USA [007], [408], [013]
Code: 494
001
125 A 163 542 28 18 .PRESSURE SENSOR
AT TANK Code: 494
001
125 A 163 542 28 18 .PRESSURE SENSOR
AT TANK Code: 806+835
001
130 A 002 477 30 01 FUEL FILTER 001
135 A 203 476 76 26 .HOSE
FUEL FILTER TO SUPPLY LINE 001
136 A 006 997 18 90 .CLIP
TO FUEL FILTER
13-14.5 001
137 A 006 997 18 90 CLIP
ON FEED LINE
13-14.5 001
140 A 000 987 01 39 RUBBER BUFFER
FUEL TANK 006
150 A 000 987 17 43 RUBBER SLEEVE
FUEL TANK [022]
001
150 A 001 990 72 82 RUBBER SLEEVE
FUEL TANK [023]
001
160 A 000 987 22 43 RUBBER SLEEVE
FUEL TANK 001
170 A 203 471 00 50 BUSHING
FUEL TANK 001
180 N 000000 0003278 HEX NUT 001
190 A 203 471 00 87 COVER
FUEL TANK BOTTOM SIDE 001
195 N 914151 1004015 SCREW
COVERING
4X12 004
200 A 203 477 00 41 HOLDER
FUEL FILTER 001
210 N 000000 0001117 SCREW
FUEL FILTER BRACKET
M6X23 001
220 A 028 997 92 48 SEALING RING 001
230 A 000 476 00 66 RETAINING RING
MOLDED HOSE [013]
Code: -494-835-929
001
230 A 000 476 00 66 RETAINING RING
MOLDED HOSE [013]
001
230 A 000 476 00 66 RETAINING RING
MOLDED HOSE [013]
Code: -835
001
230 A 000 476 00 66 RETAINING RING
MOLDED HOSE [013]
Code: -494-929
001
240 A 203 471 00 95 SHIM
TOP [013]
002
250 A 203 471 01 95 SHIM
BOTTOM [013]
006
280 A 001 990 80 54 NUT
MAINTENANCE OPENING [013]
Code: -494-835-929
002
280 A 001 990 80 54 NUT
MAINTENANCE OPENING [013]
002
280 A 001 990 80 54 NUT
MAINTENANCE OPENING [013]
Code: -835
002
280 A 001 990 80 54 NUT
MAINTENANCE OPENING [013]
Code: -494-929
002
282 A 203 471 00 79 SEALING RING
Replaced_By: A 203 471 03 79 Code: 921
002
282 A 203 471 03 79 SEALING RING Code: 921
002
282 A 203 471 01 79 SEALING RING
Replaced_By: A 203 471 03 79 [013]
Code: -494-835-921-929
002
282 A 203 471 01 79 SEALING RING
Replaced_By: A 203 471 03 79 [013]
Code: -921
002
282 A 203 471 01 79 SEALING RING
Replaced_By: A 203 471 03 79 [013]
Code: -835-921
002
282 A 203 471 01 79 SEALING RING
Replaced_By: A 203 471 03 79 [013]
Code: -494-921-929
002
282 A 203 471 03 79 SEALING RING
MAINTENANCE OPENING [013]
Code: -494-835-921-929
002
282 A 203 471 03 79 SEALING RING
MAINTENANCE OPENING [013]
Code: -921
002
282 A 203 471 03 79 SEALING RING
MAINTENANCE OPENING [013]
Code: -835-921
002
282 A 203 471 03 79 SEALING RING
MAINTENANCE OPENING [013]
Code: -494-921-929
002
300 A 000 476 37 26 HOSE
TO FUEL FILTER
11,5X3MM [404]
Code: 494
NB
300 A 202 476 68 26 FUEL HOSE
TO FUEL FILTER
1000 MM [404]
Code: 929
001
350 A 000 987 11 45 LOCKING CAP WIPER ARM
INDUCTION PIPE AUXILIARY HEATING 001
360 N 916002 2008100 CLIP
INDUCTION PIPE AUXILIARY HEATING 001



10 A 211 470 03 59 ACTIVATED CHARCOAL FILTER
CLOSED FUEL-EVAPORATION-CONTROL SYSTEM [009], [037]
001
20 A 203 470 03 59 ACTIVATED CHARCOAL FILTER
CLOSED FUEL-EVAPORATION-CONTROL SYSTEM [003], [004]
Code: 494
001
20 A 203 470 05 59 ACTIVATED CHARCOAL FILTER [005], [006]
Code: 494
001
20 A 203 470 05 59 ACTIVATED CHARCOAL FILTER [005], [006]
Code: 835
001
25 A 000 476 83 32 .VALVE
SHUT-OFF VALVE Code: 494
001
25 A 000 470 49 93 .VALVE Code: 494
001
20 A 203 470 03 59 ACTIVATED CHARCOAL FILTER
CLOSED FUEL-EVAPORATION-CONTROL SYSTEM Code: 494
001
30 N 916030 0000527 HOSE
FROM ACTIVATED CHARCOAL FILTER TO REGENERATION LINE
7.5X3 [404]
NB
30 A 107 476 24 26 HOSE
FROM ACTIVATED CHARCOAL FILTER TO REGENERATION LINE
15,3X3MM [404]
Code: -929
NB
30 A 202 476 57 26 HOSE
FROM ACTIVATED CHARCOAL FILTER TO REGENERATION LINE
370 MM Code: 494
001
35 A 203 476 03 32 VALVE
REGENERATION LINE 001
40 A 005 997 19 90 CLIP
FROM ACTIVATED CHARCOAL FILTER TO REGENERATION LINE
15.5-17.5 MM Code: 494
002
40 A 203 995 05 05 CLIP
HOSE TO ACTIVATED CHARCOAL FILTER
27-30 MM Code: 494
001
60 A 203 471 09 15 BREATHER PIPE
FROM ACTIVATED CHARCOAL FILTER TO REGENERATION VALVE [031]
001
60 A 203 471 25 15 BREATHER PIPE
FROM ACTIVATED CHARCOAL FILTER TO REGENERATION VALVE [032], [041]
001
60 A 203 471 32 15 BREATHER PIPE
FROM ACTIVATED CHARCOAL FILTER TO REGENERATION VALVE
Replaced_By: A 203 471 35 15
+008 A 000 995 40 75
+008 A 201 476 08 40 [015], [042], [007], [033]
001
60 A 203 471 35 15 BREATHER PIPE
FROM ACTIVATED CHARCOAL FILTER TO REGENERATION VALVE [009], [034]
001
70 A 120 078 03 81 HOSE
FROM ACTIVATED CHARCOAL FILTER TO REGENERATION VALVE [007], [044], [404]
001
70 A 171 476 19 26 HOSE [009], [045]
001
80 A 000 470 37 93 VALVE 001
80 A 000 470 16 93 VALVE
CLOSED FUEL-EVAPORATION-CONTROL SYSTEM
Replaced_By: A 000 470 37 93 001
80 A 000 470 32 93 VALVE
(PURGE VALVE)
Replaced_By: A 000 470 16 93 001
80 A 000 470 37 93 VALVE
CLOSED FUEL-EVAPORATION-CONTROL SYSTEM 001
90 A 203 476 01 36 HOLDER
REGENERATION VALVE 002
100 A 003 990 02 51 NUT
FASTENING BRACKET LEFT 002
110 A 170 476 15 26 HOSE
REGENERATION VALVE TO ENGINE 001
145 A 006 997 18 90 CLIP
REGENERATION LINE TO REGENERATION VALVE
13-14.5
OptionPart_With: A 004 997 20 90 [007], [039]
Code: 494
001
145 A 004 997 20 90 CLIP
REGENERATION LINE TO REGENERATION VALVE
14.5-15.5/ 8 MM
OptionPart_With: A 005 997 19 90 [009], [040]
Code: 494
001
145 A 004 997 20 90 CLIP
REGENERATION LINE TO DISTRIBUTOR
14.5-15.5/ 8 MM
OptionPart_With: A 006 997 18 90 [007], [039]
Code: 494
001
145 A 005 997 19 90 CLIP
REGENERATION LINE TO DISTRIBUTOR
15.5-17.5 MM
OptionPart_With: A 004 997 20 90 [009], [040]
Code: 494
001
145 A 005 997 83 90 CLIP
REGENERATION LINE TO REGENERATION VALVE
13-14/8.2 MM Code: 494
001
145 A 006 997 18 90 CLIP
REGENERATION LINE TO REGENERATION VALVE
13-14.5 [009], [040]
Code: 494
001
156 A 203 471 20 15 BREATHER PIPE
REGENERATION VALVE TO ENGINE 001
165 A 203 476 72 26 HOSE
PURGE LINE TO INTAKE MANIFOLD 002
180 A 000 476 01 40 CLIP
REGENERATION LINE 001
190 A 211 995 02 05 HOSE CLAMP
PURGE LINE TO INTAKE MANIFOLD 001
200 A 171 476 01 16 DAMPER CAGE
TO PURGE LINE AND VALVE
Replaced_By: A 203 470 08 16 Code: -494+M273
001
210 A 230 476 87 26 .HOSE
FLUID RESERVOIR
1600 MM [404]
Code: -494+M273
NB
220 A 005 997 49 90 .CLIP
UPSTREAM OF FLUID RESERVOIR Code: 494+M273
001
230 A 005 997 19 90 .CLIP
DOWNSTREAM OF FLUID RESERVOIR
15.5-17.5 MM Code: 494+M273
001
240 A 203 476 12 27 .HOSE
FLUID RESERVOIR Code: -494+M273
001
240 A 203 476 09 26 .HOSE
FLUID RESERVOIR Code: 494+M273
001

taylordr61

Thanks. A heavy top off on the tank by the attendant (since i live in NJ we cannot pump our own gas) must have overloaded the carbon filter. I reset the code and atleast for now it has not returned. I'll check the system visually and wait to see if I get the code again.