2001 2500hd Persistent P0446 Dtc

[stjohnso]

Truck is a 2001 2500HD 6L.

98K miles

About a month before I have to have it smogged for the first time I get an SES light, hook up HPTUNERS and I see I have a P0446.

Clear it and it comes back as soon as the onboard test is run.

Extensive internet searching and without a Tech2 scanner it looks like the EVAP Vent Solenoid is the best bet as cause (multiple TSBs on it clogging).

While I had it all apart I check flow in all the associated hoses and there seemed to be no restrictions.

I replaced the Vent Valve Solenoid with the new remote filter type, cleared code and the it came back after first test again.

My second change based on what I'd read was the Charcoal canister, replaced that and cleared code, came back again.

 

Now I'm stuck, the only other parts that could be replaced are the Purge valve and maybe the Fuel Tank pressure sensor.

I can set the Purge and Vent solenoids On and Off in HPTuners, I hear them clicking and I checked to see that they are actually open/closed by blowing through them, they are opening and closing.

 

Any ideas, at this point I don't have much else to troubleshoot.

Not a fan of taking anything to a dealer but I don't have the fittings to Vacuum test the system and seems like I need the Tech2 to really troubleshoot.

 

Thanks in advance for any input/ideas anyone might have.

Steve

[stjohnso]

Any ideas?

Thanks.

 

Truck is a 2001 2500HD 6L.

98K miles

About a month before I have to have it smogged for the first time I get an SES light, hook up HPTUNERS and I see I have a P0446.

Clear it and it comes back as soon as the onboard test is run.

Extensive internet searching and without a Tech2 scanner it looks like the EVAP Vent Solenoid is the best bet as cause (multiple TSBs on it clogging).

While I had it all apart I check flow in all the associated hoses and there seemed to be no restrictions.

I replaced the Vent Valve Solenoid with the new remote filter type, cleared code and the it came back after first test again.

My second change based on what I'd read was the Charcoal canister, replaced that and cleared code, came back again.

 

Now I'm stuck, the only other parts that could be replaced are the Purge valve and maybe the Fuel Tank pressure sensor.

I can set the Purge and Vent solenoids On and Off in HPTuners, I hear them clicking and I checked to see that they are actually open/closed by blowing through them, they are opening and closing.

 

Any ideas, at this point I don't have much else to troubleshoot.

Not a fan of taking anything to a dealer but I don't have the fittings to Vacuum test the system and seems like I need the Tech2 to really troubleshoot.

 

Thanks in advance for any input/ideas anyone might have.

Steve

[Norseman]

Any ideas?

Thanks.

 

Yup. Replace the purge solenoid on top of the intake.