Hey guys,

Have a PO449 on my Hummer H3 base and replaced the evap vent valve solenoid with a new AC Delco this weekend. The new part came with a new wire harness, took about 30mins to complete the repair. Cleared my codes and after about an hour or driving the PO449 came back. Not sure what else to check next on this beast. Anyone troubleshoot this problem yet on a 2006

JP

 

any takers?

 

Hi,
Did the new unit come with the hose or did you swap it from old one?
Did you replace the gas cap?
There is also another evap sel in the engine bay. Yes I realize it is a different code for that but could be a problem. But as stated before it is not uncommon for hose leaks in evap assembly near rear axle.

 

Check fuse 31 in underhood fuse block. If that's ok check for power at vent solenoid connector. If that's ok, you need a scan tool to activate vent solenoid and check ground control circuit.

 

1. Ignition OFF, disconnect the harness connector at the EVAP canister purge or vent solenoid valve.
2. Ignition ON, verify that a test lamp illuminates between the voltage supply circuit terminal A and ground.

• If the test lamp does not illuminate, test the voltage supply circuit for a short to ground or an open/high resistance. If the circuit tests normal and the voltage supply circuit fuse is open, test or replace the EVAP canister purge solenoid.

1. Connect a test lamp between the voltage supply circuit terminal A and the control circuit terminal B.

1. Energize the solenoid with a scan tool. Command the EVAP canister purge solenoid valve to 50 percent with a scan tool, or the EVAP canister vent solenoid valve ON and OFF. The test lamp should respond to the command.

• If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the ECM.
• If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.

1. If all circuits test normal, replace the appropriate solenoid valve.

 

This part came with the new hose, so it was replaced and the new pigtail added.

I did not replace the gas cap, however I lost my original cap at the pump last year and replaced it with a H3 locking cap, so it is relatively new (I read somewhere else where that can be an issue, maybe the new one went bad).

Did not know to check for evap under the hood, would you possibly have a pic showing the location? I will start poking around and see if I can find something that looks like it.

I was considering the carbon canister as well, is that something I should look at?

 

Thanks HUMTECH I'll also check fuse 31 and perform the ground test and get back. Thanks to both of you for the assistance!

 

Well guys, I feel pretty silly but am here to admit. Looks like someone read the fuse diagram upside down the last time he needed a spare! Fuse 31 was missing from it's location. Replaced fuse and voila. Thanks for the tip about that fuse Humtech.