P0449 code question

[Riche]

Well before I run out and replace the vent solenoid. I was hoping yall could give me a little advice on how the circuit works so I can rule out the wiring. I have tested the wires and with the key on(truck not running) I have 12V at the yellow(ish) wire (color blind so please go easy on me) now the white(ish) wire is a ground. I have no tech2 so I can't cycle the solenoid and test the wires to see if all's good. Can someone tell me how this circuit works so I can go buy the solenoid can get rid of this light? It is driving me nuts. If it is a normally closed circuit then I can assume that my wires are ok, but if it is supposed to be open and the + or - cycles the solenoid, I am in deep

Thanks,
Richard

B.T.W. this is a 2005 silverado crew cab

[J-Ri]

What solenoid is the code for? Sorry, I don't have access to a list at home.

Usually, a solenoid would be given constant power, and the computer would control the ground to complete the circuit when operation is desired. Are you checking at the solenoid, or is this a relay? If you have power and ground at the solenoid, the solenoid should be operating. If it's not, the solenoid is most likely bad.

[MT-2500]

On that code it may be a problem with the VCM vent solenoid driver.
You realy need a good engine capable scanner and the repair flow chart for that code to check or test it out.
The vcm grounds the solenoid with a built in driver.
If Vcm does see the wrong voltage on solenoid ground it will set the code.
How many miles and what engine?
Any emission warranty left on it.

[Riche]

J-ri - I was checking at the solinoid with the key on engine off.

MT - the engine has 50K+ almost 60K I bought it used not re-certified

Should it be applying the ground when the key is on engine not running?
Under what conditions would the driver open the circuit?

[MT-2500]

Originally Posted by Riche

J-ri - I was checking at the solinoid with the key on engine off.

MT - the engine has 50K+ almost 60K I bought it used not re-certified

Should it be applying the ground when the key is on engine not running?
Under what conditions would the driver open the circuit?

Not real sure.
But I would say that the engine has to be running and maybe have to be moving on the road for the VCM/PC to ground the solenoid to get it to work.
Check for voltage to the positive side of solenoid with key on.
Then.
Try grounding the ground side of solenoid with key on and see if you can hear or feel it click.
Then hook a low resistance volt/ohm meter to the ground side and drive it and check the VCM/PCM for grounding it.
Good luck
MT

[Riche]

Well with the key on I have ground and hot on the wires at the solenoid. I was plugging and unplugging the connector a bunch testing the leads. I don't remember hearing it click when I plugged it up. Is the solenoid normally open? And when you turn the key on it closes the system? Then when it needs to vent the driver pulls the ground and the solenoid opens to vent the evap? I am just guessing at how the circuit works. If anyone knows feel free to chime in. I am sure I will not be the last guy to have this code.

[MT-2500]

Originally Posted by Riche

Well with the key on I have ground and hot on the wires at the solenoid. I was plugging and unplugging the connector a bunch testing the leads. I don't remember hearing it click when I plugged it up. Is the solenoid normally open? And when you turn the key on it closes the system? Then when it needs to vent the driver pulls the ground and the solenoid opens to vent the evap? I am just guessing at how the circuit works. If anyone knows feel free to chime in. I am sure I will not be the last guy to have this code.

The solenoid is controled by the ground.
Get the volt/ohm meter oni and check power and for ground.
If it has power and ground and you unplug and plug it in you should hear or feel the solenoid work.
MT

[silveradofirerescu]

how much would the procedure change for a 2002 5.3 with 217,000 on it? Where would the solenoid be located? Is this something that will really affect the performance of my truck or is it just an emission control? thanks

[MT-2500]

Originally Posted by silveradofirerescu

how much would the procedure change for a 2002 5.3 with 217,000 on it? Where would the solenoid be located? Is this something that will really affect the performance of my truck or is it just an emission control? thanks

New problem start a new thread.

Are you geting any codes
If so what code no?

[Riche]

Just for a follow up I changed the evap. vent solenoid. It comes with a new hose and bracket, just remove the bolt holding the old one, and remove the retainer clip holding the fitting on the evap canister. Piece of cake. I was fortunate that my problem was the solenoid. I tried to plug and unplug the wire to hear the new solenoid click, but I could not here anything. So I guess if you have 12V and a ground on the wires at the solenoid when the key is on then the driver should be o.k. and the solenoid is defective. Thanks for the advice it helps sometimes to talk things through before you jump in feet first.

[MT-2500]

Thanks for posting back how it went.
Glad you got it figured out.
MT