P0446 code?!?! 😡😡😡
 

Anyone with 04 GMC Sierra pick up truck have trouble with the eve app system? I’ve had my truck in two different shops spent about $1500 and replace just about every part on the Evap system except for the computer ECM.
Every time the shop replaces a part the check engine light stays off for a month or so and then comes back on. The last time the light stayed off for after about 250 miles and then came back on.
Last time in shop they “flashed the ECM”
I was told that the next time it comes back on it probably needs a new ECM. Do these trucks have a history of bad ECM’s?

Any help appreciated?

Re: P0446 code?!?! 😡😡😡
 

These guys are using the parts canon approach. It's highly unlikely the PCM is your root problem.

The EVAP readiness test takes a while to run that's why the money light stays off.

Diagnose this and fix it. If a tech can't diagnose and repair a Purge and Seal GM EVAP system they're a poor mechanic.

P0446 is set when the car's computer believes (either correctly or incorrectly) that there's a problem with the vent valve.
I've had plugged up canisters, screwy vent valves, and bad fuel tank pressure sensors cause this error.

Re: P0446 code?!?! 😡😡😡
 

Do you use the updated evap part gm provides?

https://downloads.innova.com/tsb-fil...00/2380966.pdf

#02-06-04-037F: DTC P0446 (Restricted/Blocked
EVAP Vent Path) Set, Check Engine Light On (Replace
Evaporative Emission (EVAP) Vent Valve Solenoid
Assembly and Add/Relocate Filter Box Using Service
Kit) - (Aug 5, 2009)

I just fixed this problem. I installed the updated evap part, a new gm fuel pump and the PO446 code was gone.

Re: P0446 code?!?! 😡😡😡
 

It depends on where you're driving.
The updated kit is intended for dirt road drivers. I primarily drive it on pavement so I use the less expensive original style.

Re: P0446 code?!?! 😡😡😡
 

Thanks I’ll have to check on this part. I mainly drive paved roads also seldom dirt ( just FYI)

Re: P0446 code?!?! 😡😡😡
 

The TBS calls to route the updated EVAP vent outlet above tranny. I didn't do that. I ran it up near the gas tank inlet filler.

Also the EVAP valve is much easier to service now as it is on the outside of the frame.

Re: P0446 code?!?! 😡😡😡
 

Just recently had this issue on a 2003 GMC, After watching some videos on you tube, Eric at South main auto is a good resource I purchased a reasonably priced bi directional scanner. With this unit I was able to confirm the vent solenoid was bad ( replaced that part 4 years prior). The money light came back on some more testing and the fuel pressure sensor was not functioning ( fuel pump replaced about 2.5 years ago with a non oem pump assembly and had a cheap sensor ). Replaced sensor and drove the truck long enough for to pass a new York state inspection. Just remember Just because a part is new does not mean it is good.

Re: P0446 code?!?! 😡😡😡
 

True that! It’s sad that quality has suffered over the years

Re: P0446 code?!?! 😡😡😡
 

NEW is an acronym. Never Ever Works. :lol:
Not quite as bad as that but sometimes it seems like it's close on some parts.

I have thought about running the intake side of the vent valve up to the clean side of the air filter box.
I've run the vents from the charcoal can, axles, transfer case, and transmission up to the clean side of the air filter on my trail rig using Ni-Copp and rubber lines.