timbolio

I have seen may posts with this issue but none that answer my question that i have come across yet.

i have a 01 civic lx 2 door and recently got the code 1457 and followed the honda service manual i have and found that i have a vent valve that will not go shut since i don't have 12v pin to pin. my manual doesn't have a vent valve even listed in it so i am just troubleshooting the same as the purge valve. i would have to assume it was a broken wire or problem with the ecu since i don't have the ground loop but when i forced the contact with a otc tool the solenoid closes and i have 12v pin to pin. this leads me to think there is something else wrong possibly the fuel tank pressure switch which might be a pre-req to closing the vent valve. if anyone has a better service manual with the vent valve and tank pressure in it or knows if it is a pre-req and how to test its functionality i would really appreciate any help.

so just to recap i have already replaced the purge valve and am now getting a good vacuum and i tested the canister and i tested the two way valve. when i have the car running and cover the vent valve output i build vacuum as i am suppose to and when i force the output from the otc tool the valve works perfectly. any help from someone who know the answer would be awesome.

ezone

Vent is also known as CVS or Canister Vent Shut. Valve is normally open until activated, then it shuts and seals.


You NEED to know if you are missing the power or the ground.



Power is supplied on the blk/orn wire from fuse #4 in the dash, and it shares power with the bypass solenoid,

ground is supplied by the PCM on the light green/red wire whenever it wants to apply the valve.

It MIGHT only activate the valve during an evap self test.

timbolio

i know how the vent valve works it is not going closed so no vacuum is being pulled

i have no ground that is why the solinoid is not energizing. i am not sure what logic makes the ecu call for the valve to go closed. i know i am hearing it might be the tank pressure switch but i dont know the steps to troubleshoot this if it does in fact have something to do with valve operation.

i might go to the honda dealership and see if i can talk to a mechanic that may know since this issue is never mentioned anywhere.

ezone

Now that makes sense to me LOL.

Wait a minute..... Did you say your scanner is able to activate the CVS through bidirectional controls?
So the PCM and the wiring both are OK.

Done.

Did the valve click? They are loud enough to hear pretty easy when they are working.

Does the valve actually seal when it clicks on?

Like I said, it may only be used during the EVAP self tests. It may not be used during regular driving conditions.

Your scanner may not be completely compatible, but then I have never used your brand on one of these cars so I don't know that for sure.

The system uses a pressure sensor, not a pressure switch. Sensor should read around 2.50v @ atmospheric pressure, +/- a little for altitude changes. Voltage drops as the tank is pulled into a vacuum.

Their HDS scanner can manually actuate each of the solenoids so you can hear them click, or test each as needed if one doesn't click, and it can force an EVAP self test to run on demand (called a "function test" on the scanner).



Hey just for laughs, here's pics of a CVS valve that's rusted bad enough to leak out the seams:



This was done with about 1 PSI regulated pressure on the system and spraying DAWN dishsoap mix all over to leak check with bubbles.


You already replaced the purge valve, did you check if it had any charcoal particles clogging it?

timbolio

yea i was able to do a generic test with the scanner but i think you are correct it is not fully compatible.

yes i could hear the solenoid click but also i tested it and it is sealing perfectly which surprised me but it did.

as for the pressure sensor i was able to find a little bit of info on it that is what you said about running 2.5 i just have to go back and test it out and see what i get i just dont know if it has anything to do with closing the valve.

i cant see that vent being open all the time or there would not be a vacuum being pulled on the canister to get the fumes into the engine and also it would make it impossible for the troubleshooting steps in the honda service manual to work but like i said i am not 100% sure.

wish i had this section of the honda service manual from a north american manual that included the vent valve and pressure sensor.

thanks for you input though

ezone

The PCM will only put the canister under vacuum during the leak tests.

The CVS is left open most of the time, the system is set up to pull fresh air through the canister during purge conditions.

It closes the CVS to perform the EVAP leakage tests.

The bypass solenoid (BPS) separates the fuel tank from the charcoal canister so the system can determine which section might be leaking.

BPS open will let vacuum be applied to the gas tank for the tank leak test, and the BPS is closed during the canister leakage test.


HTH

Leejm12

Colin42

Can you repeat that in English?

Leejm12

ezone

In the factory authorized scanner ware, you would find it in the list of options below DTCs and data list, called inspection.

Of course if you are trying to use a bootleg (unauthorized, illegal) hds program or scanner from someplace like China, all bets are off. You're on your own.

It's English. Do you speak Honda, bro?

Colin42

I didn't know what HDS was, I'm not a master guru like you