98 Hyundai 1.5l code P0446

Merry Christmas to everybody.

I am having a problem with the check engine light coming on, code P0446. So far I checked the purge valve, the canister close valve, the one way valve, the filter and the vent pipe. All is ok, did vacuum test and used 12v to check the solenoids, also just for kicks I replaced the gas cap. All is working but code still coming on. There was a repair that was made to the plug on the canister close valve but I checked continuity and is all ok, I blow the lines with an air can, gas came through the pipe. I am suspecting the ECM now. Is there anything else to be done ?

Thank you for your reply.

98 Accent 1.5l auto 160k miles

Of all the systems on a car of today the evap emissions system is most likely to have a TSB about problems with it,let me go take a look real quick.

EDIT: as expected there is a 14 page TSB about how to diagnois evap codes (including P0446). I did not read the entire TSB but I think you should (and take a look at other evap TSB’s)

Hello, thank you for your reply. That was the TSB that I used to troubleshoot the system. I am leaning towards a missing close command from the ECM to the vent valve, since the purge valve works. I used all the material that was on the hyundai tech web site, but came to a stall on this.
Thank you

I have already admitted that I did not read the TSB in its entireity, is a defective ECM an indicated possibility in the diagnostic flow chart?

Thank you for your email. There is a possibility that that could be the case. My wife remembered that the other owner told her that she “could not fill up the tank…Just a little gas…”. She gave me the car with the yellow gas light on. I think she had problems in the past with that. There is valve in the tank that was supposed to break the vacuum and pressure in the tank but may be faulty - maybe have to drop the tank to find it. The wire that goes to the vent valve solenoid was not in good shape and someone tried a repair in the wiring itself - too many people tried different things on this car, I am thinking about how to see if I can get a voltage reading from it. I think I will connect a light to the circuit and drive the car to see if it will blink. I know it uses 12vdc so probably it will work. This way I can check the ground and the power connection at the splice. For now I removed the return to the intake and isolate the charcoal from the engine,because it was messing up the fuel trim in the ECM and making the car to stumble and die - gas was coming into the engine - the charcoal must be full of it… It gave me another code, a large leak this time, but I know it is because it can not get engine vacuum at the pressure sensor. Don’t you love troubleshooting ?
Just for kicks, when I replaced the spark plugs, it had two sets of ngk’s and ac delco there with a gap of 0.055 + and wire #1 read 48k ohms when it was suppose to be around 4.6 to 4.8; the timing belt was stretched (when you put at the timing mark on the top has 1 tooth off on the bottom mark) and with 159k miles It is amazing it survived 'till now. It fixed another problem as bonus: the rear Ox sensor was reading faulty due to low upper voltage limit (1.4v instead of 1.44v) so I do not have to mess with that for now.
Thank you for your email.

With KIA in 2004 we saw a lot of Spectras with evap codes. The cars were in the 98-2003 range) I believe there is technical information about this but I get a “file cannot be found” message when I try to access it (OVRV valve I believe). I remember changing the valve on top of the tank (that directed vapors towards the charcol canister) and in almost every case this did it. We performed no diagnostic work at all as the manager was the type of once he saw a trend in “cause and cure” he wanted no time spent on diagnostics. I spoke with a KIA Tech support person about what we were doing and he thought we were full of bull for changing this valve for this problem. Some cars had a plate under the back seat you could use for access or you could lower the tank a bit. I wish I could remember the procedure better but it is pretty hazzy.

I do remember a rather humerous event caused by lowering the tank to change this valve. Well on one car (of course one that I did) we still got a “minor leak” error code. It turns out that the tank was only being held in by the rubber filler hose during this repair and I stretched it so far it ripped. Talk about low quality rubber.

There is/was an actual recall on your car, this recall involved a new gas cap as the old allowed too high of pressure to develope in the tank. You must have seen this recall if you looked at the other TSB. I seem to remember a TSB on filling problems also,did you check? KIA had a lot of trouble with evap systems and with Hyundai being the parent company I would think there is reason to apply info across the line.

Thank you for your reply, happy new year to you and your family. There is a relieve valve at top of the gas tank. In the flow chart it is to be checked, I will do as the weather gets warmer. The line coming to the canister was full of gas and the canister was flooded. It is easy to replace but I think a little too expensive for what it is. Being a dealer’s choice reward item there is no option here. i did it by filling up the tank, although I stopped at the click but it is customary to round it up here in NJ. I found most TSB at the Hyundai web site www.hmaservice.com. I have the new and improved gas cap that does not allow the gas tank to be damaged. It is an underpowered little car to drive and the Mitsubishi engine responds very well to a little TLC. Thank you for your reply. Happy new year to you.