Chevrolet Repair Questions? Ask a Mechanic for Answers ASAP
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?
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).
If your scan tool has a generic functions menu command the evaporative vent solenoid on/off, listen for click at the vent solenoid.
Pin 45 is a ground from the pcm:
It controls the solenoid by providing a ground when commanded on. You should check for resistance between the pcm connector and the evap connector.
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.
If you have good power then you have eliminated half of the possibilities and your problem has to be in the ground wire.
Ok, sounds good.
Did you clear the code?
It sets on the first key on cycle or after driving for a minute?
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.
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.
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.
I'm sorry. I don't know what you mean.
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.
I'll be on here tomorrow. Just open this window back up and we can go from there.
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.