Cannot erase code P0449

Tiny
AGGIE826
  • MEMBER
  • 2008 GMC SIERRA
  • 5.3L
  • V8
  • 4WD
  • AUTOMATIC
  • 115,000 MILES
Last year I replaced the evaporative emission control solenoid, and the code was gone and now it's come back. Can you plese send me a diagram of the evaporative emissions system and procedure on diagnosing. Thank you
Monday, July 4th, 2022 AT 5:36 PM

5 Replies

Tiny
SQM
  • MECHANIC
  • 6,383 POSTS
Hello,

This could be due to an issue with the wiring as well as components.
I have attached the diagnostics for the code P0449 below for your reference. Also included is the EVAP hose diagram.

Let me know what you find or if you have any questions.
Thank you.
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Tuesday, July 5th, 2022 AT 9:25 AM
Tiny
AGGIE826
  • MEMBER
  • 18 POSTS
You guys are great but most of the advice requires an upscale can scan tool which most DIY like me do not have. I tested the purge valve, and it is holding suction vacuum and can actually hear and feel it modulating. I replaced the hose from purge valve all the way to canister. I could feel the vacuum at the end of hose. I removed the evap emissions canister solenoid and tested it with the 12 volts from the battery and got a strong clicking sound and could see it visually move. It is also holding 15lbs of vacuum on both side of solenoid when closed. To me it seems like both purge and emission solenoids are good. I could not get the emission solenoid to activate when terminal is plugged into it. Red wire is giving power to solenoid but the white wire that goes to ECM pin 61 does not seem to be working. If I take a wire from battery ground to the white wire on terminal I can get the solenoid to engage, but the ECM most not recognize that it's working because the wire is not going into the ECM. I cut the white wire by the terminal because it looked broken inside, and it was. Spliced the wires together and it seemed to work and allow me to erase code. Next morning the code is back again. Its driving me crazy/ What now?
Thank you.
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Wednesday, July 6th, 2022 AT 5:25 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 42,895 POSTS
The code P0449 means you could have a vacuum leak on the feed side of the valve, check out this video and you can see what I am talking about:

https://youtu.be/iH92vcUWJzs

Please run down this guide and report back.

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Friday, July 8th, 2022 AT 10:26 AM
Tiny
AGGIE826
  • MEMBER
  • 18 POSTS
I checked for vacuum leaks and replaced some hoses no change. I tested both the purge valve and evaporative solenoid, and both were good. What I found was that the white wire was bad going to the evaporative solenoid. I could make the solenoid work if I connected a wire from the ground of the battery to the it. But the code would not go away because the signal was not going back to the engine control module. Once I fixed the broken wire the code went away. Thank you for your help.
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Tuesday, July 19th, 2022 AT 1:24 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 42,895 POSTS
Nice work, we are here to help, please use 2CarPros anytime. Thanks for getting back to us!
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Wednesday, July 20th, 2022 AT 12:30 PM

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