evap code that wont go away po449 help

[Baja272]

i was wondering any one could maybe steer me in the right direction. I have an 08 Yukon 5.3. the po 449 code started a month ago.. I did a little reading and replaced the purge solenoid with the new update one and wiring pigtail that goes in front of the gas tank. reset the code and it stayed off to for about a week.. ran the code again, po 449 again. so I replaced the solenoid on the engine. reset the code.. [and for good measure I added seafoam to the tank] light came right back on a couple of hours later, scanned the code. 449 again. I threw a gas cap at it for could good measure. reset the code.. came right back on.

I have gone back and put the GM solenoid back on the engine and I am back to the light being off for a couple of days. I have rechecked all connects. they all seem fine. the truck has about 75k on it. it is bone stock with the exception of laser iridium plugs.

the only thing I can thing to do from here is a smoke test which I will have to take to a shop to do.. anyone have any ideas before I go that road? thank you for the help.. Rich

 

[OR VietVet]

This code is a generic powertrain code. It is considered generic because it applies to all makes and models of vehicles (1996-newer), although specific repair steps may vary depending on the model.




The Powertrain Control Module (PCM) / Engine Management Computer (EMC) / Engine Control Module (ECM) has detected a fault with the circuit that controls the vent for evaporative emission systems vapor.

As fuel sits in the tank it lets out fuel vapor, while driving this vent opens and allows the vapors to be circulated into the engine intake manifold, a charcoal canister or into the atmosphere, depending on the vehicle. This vent valve is apart of the simple, yet complicated evaporative emissions system.

Symptoms

Symptoms of a P0449 DTC will include Malfunction Indicator Lamp (MIL) illumination, you will likely not notice any other symptoms.

Causes

Potential causes may include:
•Faulty vent valve
•Wire/circuit issue
•PCM/EMC/ECM fault

Possible Solutions

Some steps to take to diagnose and repair this trouble code include the following:

Check your fuses, there may be a fuse that powers the vent solenoid.

Check for a rubbed-through or chafed wiring harness. Check both wires to see if they are shorted to each other, to ground or power.

Visually inspect the vent valve for cracks or damage.

Trace the wires to and from the PCM/EMC/ECM and check for continuity continuity using a digital volt ohm meter (DVOM).

If you have access to an advanced level scan tool, actuate the valve while reading power and ground at the connector or by simply using a bulb wired to both terminals, it will light up if power and ground are OK.

Using a DVOM, check the resistance of the vent, in most cases the resistance reading should be low, refer to the manufacturer's specification or compare it to a new one. Too high or low a value indicates a faulty coil inside the valve, thusly meaning replacement is necessary. This code seems to be prevalent on Dodge, Chrsyler, and Jeep products. In those cases the vent valve was bad. With GM products (specifically pickups), GM has released a new updated valve assembly.

Finally, remove the valve, you may be able to access the pintle inside and it simply could just be sticking from fuel residue. Clean it and retest.




If all these tests fail you then may have to do the smoke test. Check for any chaffed wiring though.

 

[jcnaranjo]

Where can I find this vent valve. I am having the same issue. Thanks.


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[Baja272]

the valve I located infront of the tank at the rear of the truck.. before you replace it look about the front drive shaft and see if it has rubbed through a harness there.. that was 280 lesson learned.