EVAP Circuitry & charcoal canister, Volvo 850

yojaywuzup · Post by **yojaywuzup** » 06 Feb 2011, 21:05

Hello,

I have a 1997 850 non turbo and I have been having an evap problem for quite a while now. The charcoal canister I have is the square one, which surprisingly has a GM stamp on it( Didn't know GM supplied volvo parts back then), I have also replaced the purge valve with one from FCP with no success. I have read in several places that the purge valve is actuated once the vehicle is turned on and applies 12volts to the purge valve. The readings I get at the connector are 5.87volts. Is the voltage supposed to be 12volts in this vehicle or is it really actuated with 6 volts? I also disconnected the canister vent valve and this had no effect on the operation of the car. I know that if I reset the codes in the car, the engine seems to run at a slightly higher idle until the check engine light comes back on and I get the P0446 code again. Is there anything I should be checking next? I want to check the connection at the PCM, but I also read I have to have the battery disconnected for at least ten minutes before doing so. I'm trying to get this car fully functional and any help and advice would be greatly appreciated.

Thank You All

PS.. Thanks to this site I have to date, repaired the ABS control module, replaced control arms, replaced odometer sprocket, replaced the blower motor and repaired the blower motor resistor.
Items on the to do list thanks to this site : rear suspension delta link replacements, front and rear suspension replacement, and ultimately implementaion of the ipod input into the sc816 stereo.
Thanks to everyone for all the very helpful posts.

Post by **DGM** » 07 Feb 2011, 13:08

The EVAP valves are labelled 8/18 & 8/43 on the electrical diagram.

When relay 2/32 operates, the valves are connected to 12Volts ...if i understand the diagram correctly

.

The code P0446 is associated with the canister vent valve (8/43). The valve can be defective. Also it is a good idea to verify the electrical contacts and its wiring.

: Mod view ECU Evap valves.JPG (363.83 KiB) Viewed 3470 times

These links will provide more information on the subject.

http://www.ricksfreeautorepairadvice.co ... alfunction
http://www.obd-codes.com/p0446

https://www.matthewsvolvosite.com/forums ... =1&t=31771
https://www.matthewsvolvosite.com/forums ... 46#p143709
http://volvospeed.com/vs_forum/index.ph ... ode-p0446/

yojaywuzup · Post by **yojaywuzup** » 20 Feb 2011, 16:29

So I finally got the opportunity to get back to this and here is what I found so far. I checked the resistance at the canister valve and the evap valve and they both seemed to check out fine. I checked for broken hoses in those areas as well since I saw a few examples of cracked hoses at the pick and pull and my hoses looked pretty much new. I also checked the wiring going from both valves to the ECM and they rang out fine. I have been unable to locate where the common ground is between these two valves as everything I have found refers to a common ground point, but I am at a loss there. I also checked to see what voltage I was getting at the canister valve when the car was turned on and I didnt get any voltage change there either off or on. This leads me to three possibilities at this time, the ground some where is loose, that relay that supplies 12v is not working and I do not know where that thing is either, or my ECM is not providing he voltage needed to actuate the valves. Let me know if I'm off track here guys, and any guidance regarding to the location of the ground or the relay would be greatly appreciated.

Thanks

Post by **jimmy57** » 20 Feb 2011, 19:07

The valves are actually grounded by ECM and 12V power supply is from relay 2/32 as DGM said in his reply.
5.87V on the side controlled by ECM is not good as that would likely mean ECM transistor power stage circuit for the canister close valve is bad .

yojaywuzup · Post by **yojaywuzup** » 20 Feb 2011, 20:46

I guess I'll try and hit up the pick and pull in the morning and see if I get lucky there. I'll post an update when I do. Thanks Again.

Post by **jimmy57** » 21 Feb 2011, 11:59

WHOA!!!!!
The 5.87 is OK since the EVAP is pulsed. IF it were held open continuously it would read close to 0V on one pin and 12V on the other. WHen the ECM operates it is is a variable duty cycle pulse and higher flow signalling may go to 9-10V and lower signalling could be 2-3 V and it is off for periods where both pins would read 12V.
Your EVAP signal is fine.

yojaywuzup · Post by **yojaywuzup** » 21 Feb 2011, 14:08

I guess it was good I didn't find a match at the yard... lol So what would be causing this P0446 since I've swapped out the purge valve, canister valve, canister, and just about all the hoses ( havent done the ones that go the the fuel tank yet? I have still never seen any voltage at the canister valve whether the car is on or off and the old canister tested fine when I used an old connector from a donor car and put 12v to it. I heard the click of it actuating, the evap did as well. I'm stumped here. What do you think?

Post by **fields 100** » 07 Sep 2012, 13:45

jimmy57 wrote:The valves are actually grounded by ECM and 12V power supply is from relay 2/32 as DGM said in his reply.
5.87V on the side controlled by ECM is not good as that would likely mean ECM transistor power stage circuit for the canister close valve is bad .

I think I have the same problem-the canister vent valve does not close during the vac. test period.
As a part,the valve is completely operational, but I can not get switched ground to the ECU. Do not think though it is an ECU
as I can not get continuity between any of the ECU pins and the control ground terminal at the valve.
The 12v at the valve is present. Also, for some reason this ground wire is of the brown color.
Any thoughts? Thanks.

chepada · Post by **chepada** » 08 Sep 2012, 23:50

I also have the same problem with my 98's70, PO455 EVAP gross leak, took it to the steeler, they did the smoke test they did not found a leak , cleared the code , it comes back in a few days the same code. they also did the evap test with the laptop and it pass but for some reason the check engine light is on, so I did my own checks if I clamp shut the hose coming from the charcoal canister to the shut off valve mine is next to the fuel filter right rear wheel and drive the car for a few days the check engine light does not come back after the drive ciclo is completed, as soon as I take the clamp off the code comes back, so I think shut off valve is bad, I replaced it, it did not work, still po455 on dash, I tested the old valve it only operate when 12v is apply, the connector in the car reads 5.87v, I check my wife car is not a volvo but it have a shut off valve and it reads 12v with the key on. I check every relay under lower dash and under the hood driver side ,none of them supply power to the valve, I starting to think to drive the car wit a hose clamped so the light stay off but is a pain to fill the fuel tank, thanks for reading.