p0449, p0446, p0451 Evap codes

[RichardRS]

Looking for some advice. I have these 3 evap codes p0449, p0446, p0451 and cant seem to find the source. Ive replaced the vent solenoid and the purge solenoid nether changed any codes.

 

Truck is a 2013 GMC Sierra 1500 SLE 5.3 V8

Edited Saturday at 11:31 PM by RichardRS

[richard wysong]

Welcome to the Forum! Always post the code definitions along with the codes. there are over 18000 possible codes, no one remembers them all and most will skip over your post rather than look them up

[davester]

charm.li (website) has GM's diagnostic procedures for each of those codes.  GM recommends working them one at a time, lowest number up.

[B07]

Glad I found this post before posting a question.

My ‘09 has been throwing those codes and P0442. I replaced the gas cap as it was trashed to begin with and the purge solenoid valve under the hood but still get the code every now and then. Dealership said I need to replace the vent lines as the previous owner use cheap fuel line that feels more like a balloon. They also said the charcoal canister and the “canister vent solenoid/service kit” so it relocates the filter up by the top of the transmission. Vent solenoid is cracked as the previous owner just let it hang loose. Too lazy to put it back on its bracket. If I put it on there the hose kinks and I thinks causes a whistle when I fill up. 
Only issue is the parts guys can’t tell me which one I need as it shows two styles. One has a jointed section. Which should I use? 
Thanks. 
I apologize for hijacking the thread

Edited 22 hours ago by B07

[davester]

they look to have significantly different tubes, so crawling under the truck and looking should tell you which you need.

[carkhz316]

On 8/22/2026 at 7:20 PM, richard wysong said:

Welcome to the Forum! Always post the code definitions along with the codes. there are over 18000 possible codes, no one remembers them all and most will skip over your post rather than look them up

Ain't nobody got time for that. The code numbers are sufficient. Google, service info, Chiltons, will all easily elaborate on the definitions. Anyone thats been working on cars for a hot minute will know these very common, as well as global OBD standard, codes with not much else given.

 

 

On 8/22/2026 at 6:15 PM, RichardRS said:

Looking for some advice. I have these 3 evap codes p0449, p0446, p0451 and cant seem to find the source. Ive replaced the vent solenoid and the purge solenoid nether changed any codes.

 

Truck is a 2013 GMC Sierra 1500 SLE 5.3 V8

You have a wiring issue, as P0449 is a circuit fault. Focus on finding that, and the other two DTCs which are rationality based, will likely be resolved too.

[B07]

13 hours ago, davester said:

they look to have significantly different tubes, so crawling under the truck and looking should tell you which you need.

I've been under the truck several times but it still has the same original parts minus the tubes as the previous owner cut it all out and used cheap gas line hose and it is soft and any movement causes it to pinch or kink and stops vapors from moving through the system. Trying to find someone who installed the updated relocation kit and which one of those two they used. Prefer not to use rubber hose where it's not needed. 

Edited 7 hours ago by B07

[B07]

Smoke test the system. You can buy a cheap smoke machine from Amazon and within a few minutes if there's any leaks then you find the problem if there's no leaks you have two choices. Trace it out for electrical issues or replace everything and then see what happens.

 I'm about to replace everything thanks to the previous owner butchering all the lines under the truck.