EVAP P0446

[TomO]

Check engine light came on this morning. Code P0446 - EVAP. Online I’m seeing mixed starting points on this 1. What do you all suggest? First time driving it on a cool morning in Indiana - guessing this Texas truck didn’t know what to do with this dense Indiana air!

2003 suburban 174k.

 

[99Sierra2500]

P0446

SYSTEM DESCRIPTION
This DTC tests the evaporative emission (EVAP) system for a restricted or blocked EVAP vent path. The control module commands the EVAP canister purge solenoid Open and the EVAP canister vent solenoid Closed. This allows vacuum to be applied to the EVAP system. Once a calibrated vacuum level has been reached, the control module commands the EVAP canister purge solenoid Closed and the EVAP canister vent solenoid Open. The control module monitors the fuel tank pressure (FTP) sensor for a decrease in vacuum. If the vacuum does not decrease to near 0 inches H2O in a calibrated time, this DTC sets.

 

[TomO]

Some good info here - both in the video and in the comments.

 

[ORVietVet]

Good videos. There have been literally millions of the purge valves sold because of it's location.

 

[TomO]

Plan on doing new purge valve, vent valve & gas cap. I’ll probably blow out the lines and clean the charcoal canister as well. Is there a special tool to disconnect the hoses?

 

[TomO]

If that doesn’t do it it’s probably the tank pressure sensor.

 

[TomO]

Decided to dig in a little more - I might be changing my plans.

Looked at the scan from O’Reillys again - it actually suggested starting with the tank pressure sensor.

FYI - the guy in this video is slightly unhinged!!

 

[TomO]

What’s the best tool to remove evap hoses? I know they can come off with a screwdriver but I’d like to mitigate my risk of breaking 1.

 

[TomO]

I’ll start out saying I know I’m all over the place with this 1! Waiting on parts to show up has me thinking…here in Indiana we don’t have emissions requirements. So I’m thinking an evap delete is an option. Has anyone done it? Thoughts on doing it?

 

[99Sierra2500]

We have emissions in the Region and Indy. Would a delete be easier than just replacing the switch? I don't know what would be involved.

 

[ORVietVet]

What’s the best tool to remove evap hoses? I know they can come off with a screwdriver but I’d like to mitigate my risk of breaking 1.

Pic of the connection(s) you are trying to remove. Have you looked at you tube?

 

[TomO]

We have emissions in the Region and Indy. Would a delete be easier than just replacing the switch? I don't know what would be involved.

Pros: permanent fix, remove something not needed.

Cons: maybe a gas smell? not sure what else?

I didn’t mention this, when I had an alignment last week I talked to the guy that ran the shop (big GMT800 fan, has several) he told me in his experience the foam that retains the charcoal in the canister tends to let loose around 200k. He highly recommended I replace that too (part I’m waiting on). When the foam drys up/lets loose it dumps charcoal pellets into the entire system and is a major chore to clean out - hoping I’m not there!

 

[99Sierra2500]

Pros: permanent fix, remove something not needed.

Cons: maybe a gas smell? not sure what else?

I didn’t mention this, when I had an alignment last week I talked to the guy that ran the shop (big GMT800 fan, has several) he told me in his experience the foam that retains the charcoal in the canister tends to let loose around 200k. He highly recommended I replace that too (part I’m waiting on). When the foam drys up/lets loose it dumps charcoal pellets into the entire system and is a major chore to clean out - hoping I’m not there!

GMT800's are popular here, I see them everywhere, it's just that they are rusty. I have heard those pellets from the charcoal canister are a bummer to clean out. When things go bad, people sometimes just replace everything. I don't know how much it has to do with the function of the vehicle, though to get rid of it, I think the PCM has to be reprogrammed, and most places aren't going to want to do that. Emissions stuff is a chore to deal with, though it is also illegal to modify or remove.

 

[TomO]

GMT800's are popular here, I see them everywhere, it's just that they are rusty. I have heard those pellets from the charcoal canister are a bummer to clean out. When things go bad, people sometimes just replace everything. I don't know how much it has to do with the function of the vehicle, though to get rid of it, I think the PCM has to be reprogrammed, and most places aren't going to want to do that. Emissions stuff is a chore to deal with, though it is also illegal to modify or remove.

Didn’t even think of the legality of it. I assumed it’s an old truck + with no emissions check = no one cared! Haha

Guess that helps make the decision - I’m going to have about $250 in replacing all the “moving parts” in the system.

 

[99Sierra2500]

Didn’t even think of the legality of it. I assumed it’s an old truck + with no emissions check = no one cared! Haha

Guess that helps make the decision - I’m going to have about $250 in replacing all the “moving parts” in the system.

That could be about the same cost of getting it tuned out of the pcm. It's sort of like I have a security light on, and to get it tuned out or turned off is $175, and I'm too cheap to do that if it is just the light.

 

[Tonimus]

The dongle for tuning is $80. Can easily turn off both security and evap lights.

 

[FW_Z71Burb]

Retain your EVAP system and keep it fully functional. Don’t delete it.

 

[stutaeng]

You can disable the CEL code from popping up on your dash with HP Tuners, but sounds like @Tonimus has a cheaper/easier way...(curious what that model is BTW?) Everything will still work, you just won't get the annoying "money light" on your dash.

I wouldn't delete the actual system because you'll get very strong smells, like the old guys putting the little air filter vent breather gadget on their old vehicle gas tanks...you know, the guys running carbs and stuff...

 

[Marky Dissod]

Retain your EVAP system and keep it fully functional. Don’t delete it.

I actually agree, but if you don't EXPLAIN WHY, you sound more like you're ordering a stranger around, than sharing knowledge.

Unfortunately I don't know enough about why to be more helpful, but I thought it had something to do with preventing the tank from ballooning?

 

[Tonimus]

You can disable the CEL code from popping up on your dash with HP Tuners, but sounds like @Tonimus has a cheaper/easier way...(curious what that model is BTW?) Everything will still work, you just won't get the annoying "money light" on your dash.

I wouldn't delete the actual system because you'll get very strong smells, like the old guys putting the little air filter vent breather gadget on their old vehicle gas tanks...you know, the guys running carbs and stuff...

OBDX Pro VX. https://obdxpro.com/product/obdx-pro-vx-obd2-diagnostics-and-tuning/

PCM Hammer to read the PCM. TunerPro to modify the file. PCM Hammer to write it back. Did a VATS deactivation on mine. Took about 10 minutes altogether.