BigDog117

Hey guys i have done a ton of looking and cant get this fixed. I have a 2004 silverado 5.3 crew half ton. It threw the dredded 449 evap code. So it seems like everyone replaces the vent valve and they are good to go. Well i did that and checked my old one too, it was good and so is my new one, i changed the gas cap also , nothing has helped. I reset it and it keeps coming back. I have 12 volts the the pink wire but i have been unable to see the white wire go to ground, i have tried with the truck running but it has never cycled that i can see. I have been unable to find a drawing of where the other end of that wire goes, i have followed it along the frame and find nothing. I dont have a programer that will tell if the output is on or off. Anyone have any ideas where to go from here? I took out the PCM tonight , i read somewhere about pin 45 on the green connector goes to another connector under the fuse box or something, it had no continuity with the white at the plug for the vent. PLEASE HELP

EinST

Welcome to the forum. The EVAP vent solenoid is supplied a ignition voltage (hot in run or start) on terminal B. The PCM then grounds terminal A to actuate the solenoid:

Terminal A, WHT wire, EVAP Vent Ctrl, PCM connector C2, terminal 45
Terminal B, ORG wire, Ign Voltage, 15A 4WS fuse in underhood fuse block

The PCM also monitors the voltage level on the WHT wire. P0449 means the monitored voltage level didn't match the commanded state, i.e., voltage is present when grounded and vice versa.

BigDog117

I did check between the terminal 45 on the pcm green connector to the white wire in the back and it was open, this indeed could be my problem, my buddy told me last night his did the same thing and he had to take the large box that the solinoid connects to off and blew it out, he said its a charcoal filter or something like that?

EinST

The code concerns an electrical problem. I'd say your buddy is mistaken.

BigDog117

Does anyone have a drawing that shows the electrical on this, I am thinking about just pulling a new wire and replacing the white one, I just want to make sure that the white wire comming off of terminal 45 on the green connector at the pcm beside the battery is the other end of the white wire at the plug for the vent valve. Could it be the purge valve if that is not it?

BigDog117

ok guys incase anyone has this issue i found my white wire had a break in it. I found it about 6 inches back from the plug, Im am one very happy guy with no engine light!!

burban_fever

Hi everyone, I'm new to this forum. I have an '04 Suburban LS w/5.3L, and I'm getting random "tighten filler cap" messages. No CE lights. Is this the same problem that you're calling the P0449?

Thanks!

EinST

Welcome to the forum. I doubt it's the same problem. P0449 concerns an electrical problem. Your problem is determined from an illogical air pressure inside the fuel tank. Even if the malfunction indicator wasn't lit yet, there should be a pending trouble code. Also, try a new cap since they do go bad occasionally.

bubba army

i have a 96 1500 4.3L it has black smoke coming from tailpipe.the converter was clogged i replaced it thats when the smoke started i replaced plugs&wires and o2sensor before the converter motor is not missing any ideas what it could be

chrispy

if you are positive that the white wire is ground why not cut it at the sensor and ground it? then the other end thats not have continuity will tell you of another problem? if not just reconnect it.