Yup, you're overthinking, just drive it a few cycles , as Jim sang , keep your eyes on the road and your hands upon the wheel!!
Before you spend on the Evap purge vent valve, check for a loose or corroded wire connection!

 

My quest for "drive cycle" completion got interrupted since my last post, by a busted water pipe under the floor (luckily I cut an access hole there previously), and by the resultant sciatica and back problems after that. Did I mention the copperhead invasion after that (killed one, buried one alive!!)? So, I'm a few days behind my schedule. When I went to Home Despot to get sharkbite adapter fittings (to add a pex extension to the pipe, under the floor, where I couldn't reach, to the leaking polybutylene pipe-I'm always hesitant to reach where I can't see, because my neighborhood has a history of snake infestations), I was able to complete the O2 test. Pipe repairs completed, I rested my back for the weekend, and only backed the HHR onto my rhino ramps to await my test of the evap vent solenoid. I just now tested the solenoid, with 12v jumpers, and it clicks open and closed. I will check the signal voltage, when I go back to the garage with my meter. After that, the next test is to see if the evap vent hose is blocked. I tried to remove the connector, by pushing the white tabs, but it wont come loose. I'm hesitant to use pliers, because I have broken one before. If it breaks, what size hose can I splice into it? If the hose is clear, and the signal to vent is there, then the problem would be the tank pressure sensor? That means lowering the tank (2/3 full). If that is done, I should disconnect the battery, and...there goes my semi-completed "drive cycle" record. Could I just loosen the tank strap, and reach in to retrieve the sensor, without a disconnect?

 

evap vent solenoid = clicks on and off, ok. vent hose=blew clear, ok. checked all fuses (incl.#64? evap)= good, ok. My I/M emissions readiness has gone from yellow, with one code, to red, with four codes. Now, after checking for dtc's, I've got Po446, still there, plus Po449 MIL, Pending, and Permanent. I get no voltage from the pink wire, and .5vdc from the control wire. I should've gone to the dealer.

 

Have you looked at the tut here: https://www.chevyhhr.net/forums/how-...acement-44780/

You usually need a large needle nose on those type of connections.

When you get to the replacing part be careful with the O-ring seals, you may need to get a new one. A bad seal will cause a code.

The signal is PWM, so a VOM might not tell you anything.

 

p0449 probably means the tube isn't connected right. That is "large" leak, usually gas cap, but can be either stuck open valve or bad O-ring seal.

 

I was using a Micronta vom. How did I get the extra codes? Running it with the evap solenoid unplugged? Could I have shorted the BCM with my probes? Electrical diagnoses are not my forte; I had to get a friend re-wire my Chevelle after I fried the wiring.

 

tip for Working on it - if you are doing searches for those pesky codes you got, note that the second character in the code is Numeric, not an alpha - ie: it's p0449, not po449

 

First: PWM mean the voltage is variable, usually between 0V and .5V. Which is why a VOM doesn't tell you anything if you don't know what to look for.

The P0449 means that the OBD test tried to run but failed. As soon as that is fixed it should be good.

See my post from a few minutes ago.

 

Thanks. Numeric not alphanumeric. Anyway, I had no trouble with the vent hose on my third try; it came straight off, it easily went back on, it shouldn't be leaking. But, my scanner shows the new codes as: P0449 Evaporative Emission Control System Vent Valve/Solenoid Circuit Malfunction If the circuit is at fault, but not actually shorted-out, what is my next step? Resume my "drive cycle" attempts or go to a shop? My temporary registration expires in two weeks.

 

I got them backwards. "circuit malfunction" could mean the coils in the solenoid are shorting or broken or a wire is broken or anything in between.

What is the status of the P0446? That is what I meant in post #28.

The main listed fix for both is a new vent valve.

I was wrong about it being PWM. Look at these links https://www.obd-codes.com/p0446 And https://www.obd-codes.com/p0449