UPDATE: I got the job completed. No further help (on this topic) needed.

I read a great post about replacing the evaporative emissions system vent valve solenoid. Great write up based on a Vett with a manual transmission. I have a 2009 C6 with A6 transmission. That makes it a lot tighter trying to reach the solenoid.

I ordered a solenoid and harness on Amazon. The new solenoid has the rounded ends connector, so the old harness should attach. Hopefully the old harness is good because the new GM harness that I bought has the square connector.

Let me explain what I have done so far:
I've been working for a couple of hours attempting to get the hose disconnected from the solenoid. That isn't going so well because of insufficient room to get my hands where they need to be to disconnect the hose. I am able to get my hand in and unplug the connector, and I can also slide the solenoid off its bracket. In an attempt to provide more room, I've started working to lower the exhaust. I removed the two bolts at the back that hold the muffler up. I've loosened the clamp where the exhaust pipe goes into the H-pipe. The muffler lowered about half inch to the sway bar, and that did not provide much clearance to reach the solenoid. Also, I have the NPP exhaust, and the vacuum line to the mechanism will also restricft moving the muffler and pipe. I was unable to get the vacuum hose off. Seems that it should just slide off.

If I can find a tool that allows me to reach up and expand that spring hose clamp, I'll take that route to finish this job. Assuming I can't find such a tool, I see two options. (I've tried several types of pliers and can't get my hand in there to operated them in the needed position.)

I need some feedback regarding the options I am considering. The first is probably the easiest if there is enough existing length of hose.
1. Cut the hose as close to the solenoid as I can. Install the new solenoid and use a hose clamp that I can tighten with a long bladed screw driver.. Then put my exhaust back up and be done.
2. If cutting the hose is a bad idea, disconnect the vacuum line to the exhaust, remove the sway bar, and lower or remove the muffler and pipe. I'll need the torque values for putting the sway bar back if I do this. Can anyone provide those? I'll need to figure out how to get that vacuum line loose from the NPP mechanism. Any tips for that? If I go with this approach, I should be able to get the spring clamp off the hose and not need to cut the hose that goes to the solenoid.

Whatever tips people can provide will be appreciated.

 

Changing the vent solenoid without checking the wiring could have you going back in there again...if you can find someone with a Tech 2 or an aftermarket scan tool with bi directional capability makes checking it so much easier...you basically check for 12 volts on one wire with a multimeter and you need the scan tool to have the PCM ground the circuit to close the valve on the other wire...you can check that the PCM is grounding the control circuit by using a test light connected to battery positive and back probing the control wire...when the PCM does its EVAP test you can check the control circuit at this time and the test light illuminates !!

 

I just replaced mine.

The only way I could get the hose off was to go ahead and remove solenoid from the bracket after removing the wire connector.

Then the solenoid hangs down and it's easier to remove the clip holding the hose on.

 

Thank you for your help. I have a scan tool, but I'm not sure it has the needed capability for this. I'll read the manual. If I don't have what is needed, I was thinking that I could connect the new solenoid, clear the code with my scan tool, start the car and see if the code comes up again. If the code doesn't pop up pretty soon, put the exhaust back in place and be done.

 

I gave that a try, but I couldn't get both hands in to hold the solenoid with one while I pushed the clamp back with the other. I did however get this completed. I bought two pair of 16" needle nose pliers, one straight and one offset 45 degrees. I was able to use the straight pair to get the clamp off, then needed the angled tip to get it back on. I wish I had bought the compound joint pliers because the space to open and close them is pretty limited.

 

I got the job completed. My scanner didn't have all the capability you mentioned. So, I used an ohmeter to check the resistance of the solenoid on the new one and the one I removed. A solenoid coil should have some resistance but not infinite.. The old solenoid had infinite resistance, indicating an open. The new solenoid had 23 ohms.
I bought a couple of 16" needle nose pliers and was able to get the clamp off and reinstalled without taking the exhaust pipe completely loose. It was pretty difficult to get the hose off the solenoid once the clamp was off. That didn't surprise me, but it was a pain in the neck.

 

If you have code P0449 and an automatic transmission, it's a bit of a job to change the solenoid. If you want to make it easy on yourself, plan to removed the rear sway bar and drop the right exhaust pipe and muffler. I went at this the hard way trying not to remove the exhaust. If you attempt it without dropping the exhaust, you need long thin hands and arms and a pair of long needle nose pliers to get the clamp moved back on the hose.