CEL - P0446 Evaporative Emission Control System Vent Control Circuit Malfunction

[samisheikh]

Hi,

I just bought a 2007 Mazda 3 HB 2.3l with CEL on it. The seller told me that it was just an oxygen sensor. When I got the car, I realized that the mileage I am getting with the car is terrible(200-250kms per tank). I decided to hook up my laptop to the OBD2, and sure enough P0138(Oxygen sensor Downsteam bank 2) and P0446(Evaporative Emission Control System Vent Control Circuit Malfunction) came up.

Now, P0138 is a very quick and easy fix but for P0446 I have no idea what part to order or what is wrong with the vehicle. All i know is that the Evap system has a malfunction and the problem could be with any of the following things.

Fuel Cap
Fuel filler cap
fuel filler tube
Foreign material in fuel filler
Solenoid for Evap system
Vapor canister
PCV valve
Purge valve

Can somebody please assist me with what part should I be replacing or where should I begin with the diagnostics?

I already checked the fuel cap, and it seems to be fine and it clicks when i close it. Also the whole for filling in the fuel has a little door and it closes and opens fine as well.


Thanks in advance

[gabbygenier]

I had the same code on my car for a while. last fall i decided i had to get it fixed due to the new emission tests. i brought it to the dealer and they ended up changing the evap box in the back. i cant remember exactly how much that was as other things got done to the car at the same time. it did take them a while to diagnose as each component in the box was working fine individually. at one point they thought it might be the fuse box or the PJB that was causing the issue.

from my experience, i would bring the car to a mechanic in order to troubleshoot. seems as it would be easier that way. they had my car for 3 days to do the diagnostics on it.

[samisheikh]

I brought it to a mechanic and without even looking at the car he said to replace the Solenoid valve. Apparently it is a common problem in the Mazdas. Anyone to comment on this?

[jay93]

On my old car I got that c.e.l about the evap and brought the truck to my mechanic, he checked it out and actually tightened the gas cap and the code cleared. It was so simple but I guess it's not so simple for you

[Como]

I also have come up with this c.e.l code.
Going to go through the steps to see what will clear this code. Can't imagine how much it would cost for a mechanic to check everything related to this code. It takes a few days for light to come back on after clearing it which seems odd.

[samisheikh]

I also have come up with this c.e.l code.
Going to go through the steps to see what will clear this code. Can't imagine how much it would cost for a mechanic to check everything related to this code. It takes a few days for light to come back on after clearing it which seems odd.

I just got the evap solenoid valve replaced and erased the code, so let's see if it comes back or it will be just as bad. However I have noticed my gas mileage is much better now.

[samisheikh]

So the CEL is back with the same exact code(P0446). I will be going back this week to my local garage and getting the vapor canister changed. I will see how that pans out.

[Como]

So the CEL is back with the same exact code(P0446). I will be going back this week to my local garage and getting the vapor canister changed. I will see how that pans out.

That sucks.
Did you fix the o2 sensor?
I reset my cel and it came back again about 2 days later. Same.
I haven't noticed and degradation in fuel economy though.
Trying to determine where to start with this. I'm incredibly lucky as I just had my etest done in January and passed

[samisheikh]

That sucks.
Did you fix the o2 sensor?
I reset my cel and it came back again about 2 days later. Same.
I haven't noticed and degradation in fuel economy though.
Trying to determine where to start with this. I'm incredibly lucky as I just had my etest done in January and passed

Yeah I got the O2 sensor replaced at the same time... The O2 error hasn't come up yet so I am guessing that is fixed but this Evap thing is killing me. I did some more research into this and it could be the vapor canister or the vent valve, especially when driving in dusty places(which is where the previous owner lived).

[Tiesto]

I had this problem on my old Nissan all it was a cracked hose right where it went into the the evap box. I believe the system monitors the pressure and if it's out of spec it throws the code.

I hope it's a simple fix for you.

[TYBO]

I am having pretty much the same issues - 2007 3 GT. P0446 code. Took it to my local mazda dealer and they really couldn't tell me what was going on with it. Mechanic says that its either the PCM, Charcoal Canister or leak detection pump. I have had this problem on and off for a while now. I replaced the leak detection pump last year and everything was ok. This past winter I started having problems putting fuel in again, then when the weather warmed up I could get fuel in but now I have this P0446 code. Please post and let us know if the charcoal canister fixes your problem. Also does anyone else out there have any other ideas as to what to do in this situation??? I have no idea what to do, and it seems like the dealership wasn't to sure what the problem is either.
Thanks/

So the CEL is back with the same exact code(P0446). I will be going back this week to my local garage and getting the vapor canister changed. I will see how that pans out.

[wmzda5]

where is the leak detection pump located? How much did you pay for the part? DIY?

[yally]

I had to replace the fuel cap recently with their newer version for my 2008. No more codes so far!

[Mike]

I have the 'exact' situation as TYBO. So any feedback would be appreciate. Samisheikh, did replacing the vapor canister help?
I'm thinking of taking the vapor canister and its vent control valve out and see if cleaning it helps first. I'm guessing that's the problem. Now I just need to find an 'how-to' somewhere online.

[TYBO]

The leak detection pump is located under the rear end close to the fuel tank. I did it myself with a friend of mine who is a mechanic, but in order to do it the right rear wheel must come off and I also removed the filler neck to give myself a bit more room and im sure a few other things that I cant remember right now. But beware that it is tight up there, tight enough that if Mazda is to do it they will drop the whole rear end of the car to get to it. That could be the easiest way to get to it, but it certainly isn't the cheapest. The part itself is a mazda specific part and will retail for approx. 225-250 if I remember correctly.

[TYBO]

Hey Mike, Let me know how this works for ya!

I have the 'exact' situation as TYBO. So any feedback would be appreciate. Samisheikh, did replacing the vapor canister help?
I'm thinking of taking the vapor canister and its vent control valve out and see if cleaning it helps first. I'm guessing that's the problem. Now I just need to find an 'how-to' somewhere online.

[TheMAN]

LDPs going bad is a fairly common problem on any newer mazda

[Mike]

After laying under the car for an hour last night trying to understand the evap system, I'm still a bit confused. I can't figure out where the canister vent control solenoid is. Is it the same as the Leak detection pump? Or is it part of the charcoal canister box?
Is the leak detection pump also in charge of venting the gas tank?
There's not much info in the mazda manual regarding this part.

[wmzda5]

The easiest for you to pinpoint the cause of the cel is to get the dealer to diagnose and pinpoint the part thats needed to be replaced. I did this and paid $133 for diagnostic. Went to Magnum Parts in steeles and weston to buy the part (LDP) dealer is asking $256, I got it for like $147. The guys at the parts store are very helpful and even printed the picture of the part and where it is located in the car even before I bought the part. Made replacement of the part easier for me and saved me an easy ~$350. Dealer wants ~$500 parts and labor aside from the diagnostic fee.

[Mike]

To follow up on my problem, I gave up trying to figure it out and brought it to my local garage for troubleshooting. The diagnostic was the Leak detection pump as some of you suggested. I'm hoping that's the permanent solution. They charged me around $300 for part and labor all in. From what I've been reading, it wasn't worth my time trying to get that little sucker out of there.

[jeffjones]

sure enough P0138(Oxygen sensor Downsteam bank 2)Now, P0138 is a very quick and easy fix

How do you fix this?
I have this CEL thrown usually when it is wet outside and then it disappears later in the day, but has been coming on about 3 times a month for the last 3 months.

[ryan2.3]

2004 2.3 HB. This code (P0446) came on Monday. I checked the gas cap. Appeared to be fine and properly installed (will probably test my wife's gas cap on mine). Cleared the code and stayed away until yesterday afternoon.

Was the official solution the Leak detection pump? I found an OEM one online for about $130, but I want to be sure that this is it. Because I also found a purge valve online for a good price as well as a Bosch O2 Sensor. Though i may do the O2 sensor just because since it's about $40 and i'm pretty sure it's never been done.

Torque gave me the below report if it helps

Vehicle VIN: JM1BK143641157917
Vehicle Manufacturer: Mazda
Vehicle Calibration ID: L373ED020L3V5020

Current Fault Log
------------------
P0446: Evaporative Emission Control System Vent Control Circuit

not sure what MID's and TID's are. Figured they were similar to PID's and DID's that i deal with at work.
http://drive.google.com/uc?export=view&id=0B3eycRJGDrBTdGhaOXRzZGVkSWs

The mode report of the trouble values (since the top is cut off) are

MID:$b0 TID:$99
-
Max: -74.38335% Min: 25.19731%
Test result value: -79.93798%
FAIL
----

MID:$b1 TID:$1a
-
Max: 2mV/s Min: 8,354mV/s
Test result value: 13,664mV/s
FAIL
----

MID:$f0 TID:$cc
Manufacturer defined MID -
Max: 0 Min: 8,273
Test result value: 52,464
FAIL
----

[WriterGuy]

My 2009 Mazda 3 has this code for the second time - once in October 2013 and now in August 2014. The Mazda Dealer charged me for 2 hours diagnostic time this time and said they cannot find the cause. Possibly it is a wiring problem they said. I do not know what to do now. The gas cap was replaced by the dealer (no charge) and of course during the diagnostic the code was cleared but it came back on a week or so later. A mechanic could spend ages at $110/hr and get nowhere, as far as I can tell. Seems like bad design.

[ryan2.3]

i've cleared it a few times now and it comes back every 2 days. Unlike previous posters saying their mileage dropped significantly, this past tank was only about 75km worse than normal.