Nissan emission issue

I have a 99 Maxima that originally showed a Knock sensor error code and an evap purge control valve failure. I replaced the purge valve first and didn’t replace the knock sensor. I then checked the code to find that I now had the knock sensor code the evap purge valve code and a system vent control code. I replaced the knock sensor and that code cleared. I can’t however get the other two codes, p0446 and p0443 and can’t for the life of me get that to clear. Any help is greatly appreciated.

You need to check the wiring & power supply for the vent valve. You’ll likely need a multimeter, though sometimes a simple visual inspection can say it all.

Have a look at these for some help:

Note that both of these (as with many of the OBD codes) refers to a circuit rather than a part. Sometimes a problem in a circuit is b/c of the part. Sometimes not.

Half the time, it’s just a bad connection…it’s been 12 years…

Thanks for the info but which connection. I’ve checked the connection to the purge valve solenoid and all the vacuum lines and electrical’s under the hood and around the smog box related to the smog system. I only mention this because over the summer I replaced the starter causing me to remove the air intake assembly. I triple checked my work since this new issue started. Keep brainstorming…mine’s fried from this one. Thanks for your input.

When you say you checked, you mean you looked at it? Or you mean you put a voltmeter or scantool on it?

I haven’t put a meter to them (yet). but I did physically check them (push/pull). I guess I’m also not sure what I should read on the meter. 12V? Do I just ohm it out? Is one wire a signal and the other hot?

The above links give you a good way to test the system.
Try that first.


I’m not sure how to test the system at the ecm level…forgive me but my experience working on cars came before they started putting computers in them…Give me a chevy 350 and I’m golden.

From the above links:

  1. Using a scan tool, command the purge solenoid to activate. Listen or feel for a clicking coming from the purge solenoid. It should click once, or on some models it may click repeatedly.

  2. If it doesn’t click with scan tool activation, unplug the connector and examining the solenoid and connector for damage, water, etc. Then check for battery voltage on the feed wire with the key on. If you have battery voltage, then ground the control side manually using a jumper wire and see if the valve clicks. If it does, then you know the solenoid is working properly but there is a problem with the control circuit. If it doesn’t click when you manually ground it, replace the purge solenoid.

  3. To check for a problem on the control circuit (if the solenoid tests okay and you have voltage to the solenoid) plug the solenoid back in and remove the control circuit (ground) wire from the ECM connector (If you’re unsure how to do this, do not attempt). With the ground wire removed from the ECM, turn the key on and then manually ground the Purge valve control wire. The solenoid should click. If it does, then you know there is no problem with the control wire to the solenoid and there is a problem with the ECM purge solenoid driver circuit in the ECM. You’ll need a new ECM. However if it doesn’t click, then there must be an open in the wiring between the ECM and and the solenoid. You must find it and repair it.

This sounds really, really easy.


ok I guess after looking at it with a clearer head option 2 is the “easiest” for me. Which wire is the feed wire and which is the control? Again sorry for my ignorance and thank you for your help and patience. With that said I have another purge solenoid on order. I’ve put the old one back in and will test the code tomorrow.

The best bet is to have a repair manual of some kind. Haynes/Chilton’s are available at most auto parts stores, but they’re not always the best (in fact they can be pretty bad) but they often have this info.

The other thing to do is go to Autozone’s website, register (just an email address), plug in the car’s info, and go to the Repair Info section. You can often get the basics there for many of those electrical gadgets (wiring, voltage & resistance specs).

Thanks…I’ll check that out…I agree haynes can be helpful if you “REALLY” don’t know what you are doing…but I didn’t see anything there that helped.