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Ask Jared D Your Own Question
Jared D
Jared D, ASE Certified Technician
Category: Chevy
Satisfied Customers: 1355
Experience:  Shop Supervisor at County Fleet
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I have a 2005 chevy 1500 4.8l Im getting code po449 so I

Customer Question

i have a 2005 chevy 1500 4.8l Im getting code po449 so I changed out the vent valve and purge solenoid code is still coming back what do I do to fix
Submitted: 1 month ago.
Category: Chevy
Expert:  Jared D replied 1 month ago.

You most likely have a wiring issue. The P0449 indicates an evap canister vent solenoid problem so it you already changed it then the nest step is to go after a wiring fault. Do you have a scan tool that will command the valve to open/close?

Customer: replied 1 month ago.
I have a scan tool but I didt se any place where it would let me turn off or on
Expert:  Jared D replied 1 month ago.

Check for 13-14 volts to the evaporative vent solenoid on the Orange wire with the engine running. This Orange wire is powered all the time (even at key off).

Test the evaporative solenoid resistance, solenoid disconnected. Should have 20-30 ohms.

If the solenoid checks OK and the power feed is OK, then test the evaporative vent solenoid control wire, White.

Check the White wire from the PCM, pin 45, green connector, to C152, 12 pin connector, pin F, under the Underhood Bussed Electrical Center (UBEC).

Expert:  Jared D replied 1 month ago.

If your scan tool has a generic functions menu command the evaporative vent solenoid on/off, listen for click at the vent solenoid.

Customer: replied 1 month ago.
should pin 45 on green connector have power
Expert:  Jared D replied 1 month ago.

Pin 45 is a ground from the pcm:

Customer: replied 1 month ago.
oh ok im checking now
Expert:  Jared D replied 1 month ago.

It controls the solenoid by providing a ground when commanded on. You should check for resistance between the pcm connector and the evap connector.

Customer: replied 1 month ago.
I have power at the vent solenoid but no ground
Expert:  Jared D replied 1 month ago.

It won't ground unless you have the pcm commanding it to ground. So without a scan tool to command it the best you can do is check the continuity of that wire from the PCM to the Evap solenoid connector. You can check ohms of resistance from one end of the wire to the other. If you get OL on your meter then the wire has a break somewhere between the PCM and the solenoid.

Expert:  Jared D replied 1 month ago.

If you have good power then you have eliminated half of the possibilities and your problem has to be in the ground wire.

Customer: replied 1 month ago.
im checking some things now il get rite back to you
Expert:  Jared D replied 1 month ago.

Ok, sounds good.

Customer: replied 1 month ago.
weve gried everything engine light still comes rite back on,i even ran a ground myself
Customer: replied 1 month ago.
ran ground wire from pcm to solenoid white wire to white wire still no activity
Expert:  Jared D replied 1 month ago.

Did you clear the code?

Customer: replied 1 month ago.
comes rite back
Expert:  Jared D replied 1 month ago.

It sets on the first key on cycle or after driving for a minute?

Customer: replied 1 month ago.
sets on first key cycle
Expert:  Jared D replied 1 month ago.

That would seem like it's still a wiring issue then.

Did you test the evaporative solenoid resistance? With the solenoid disconnected it should have 20-30 ohms.

Customer: replied 1 month ago.
I did
Customer: replied 1 month ago.
also tried new part
Expert:  Jared D replied 1 month ago.

The connector at the PCM seems to be ok?

If you ran an overlay for the ground side, maybe run an overlay on the power side from the battery straight to the orange wire and see what happens.

Customer: replied 1 month ago.
he has power all the time with key on or off on orange wire side
Expert:  Jared D replied 1 month ago.

A good solid 12 volts?

Do you have an induction loop to check the amperage on that voltage feed? If the connector of that 12 volt wire is corroded then it could have 12 volts but no amps.

Customer: replied 1 month ago.
wiych is the positive number on the vent valve
Expert:  Jared D replied 1 month ago.

I'm sorry. I don't know what you mean.

Customer: replied 1 month ago.
whats the number of the positive wire coming from pcm
Customer: replied 1 month ago.
im gona check some more things tomorrow im closing for tonite ,I would like to get in touch with in in the morning how can I do that
Expert:  Jared D replied 1 month ago.

There is no positive wire from the PCM to the vent valve. Only a ground signal. The positive wire is the orange wire that comes from the 4WS fuse in the underhood fuse box.

Expert:  Jared D replied 1 month ago.

I'll be on here tomorrow. Just open this window back up and we can go from there.

Customer: replied 1 month ago.
ok thank you il pay to call you ok
Expert:  Jared D replied 1 month ago.

However works best for you works for me. We can proceed here or by phone. I get to my shop at 8:00 AM MST.