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Dan
Dan, Technician
Category: Chevy
Satisfied Customers: 23587
Experience:  Independent Shop Experience, 2 Year Automotive Diploma, & Access to Information Database
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2011 HHR LT2, 2.4L - OBD MIL Code P0449 My Enginuity Scan

Customer Question

2011 HHR LT2, 2.4L - OBD MIL Code P0449 My Enginuity Scan Tool graph shows the "Evaporative system vapor pressure" in the red at 16,382 [H2O] Also, When revving the engine past ~4000RPM, the "Commanded Evaporative Purge reads 6% with vent manually closed.
Have also found the following: Canister Vent solenoid opens and closes with 12-13VDC test source on bench: Voltage to the connector going to the rear vent solenoid ranges from 14VDC to 8VDC, however, when connected back to the vent valve, the solenoid does
not close?? I then plugged the vent side of the vent valve to simulate the valve being closed but still get code P0449. Engine mounted Purge valve solenoid works (It continually cicks and produces a slight vacuum when you put your finger on the rear end of
the purge solenoid [going back to the rear canister.] So what should I do next?
Submitted: 1 year ago.
Category: Chevy
Expert:  Dan replied 1 year ago.
The red/white wire on vent valve should always have battery voltage. If voltage is dropping lower then 12v this would either mean fuse has a poor connection, connector going to fuse box has poor connection, or connector 401 has poor connection. Here is a wire diagram to help with testing, let me know if you have more questions. Thanks.
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https://www.dropbox.com/s/hpdqzljdzf44h1j/vent.png?dl=0
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Customer: replied 1 year ago.
So, based upon my testing you would agree that both the Purge valve solenoid and the vent valve solenoid are ok, but
it is just the 12VDC connection? and does that mean that even though I plugged the vent valve to simulate that the vent valve is closed I'm getting the P0449 code because the voltage is being tested, not the actual vacuum in the system?
Expert:  Dan replied 1 year ago.
I agree and this code sets when it see's circuit/wiring problem. Let me know if you have more questions, thanks.
Customer: replied 1 year ago.
Checked the fuse under the hood and still getting ~11.5VDC at the rear floor body connector next to the fuel tank. Vent valve is still not closing (remains open even with the 11.5VDC current. Still getting 11,383 H2O vapor pressure when I run above Idle Just in case, replaced the vent valve solenoid assembly - What's next? Is there another fuse or connector I should be looking for? Could it be the tank sensor?
Expert:  Dan replied 1 year ago.
Backprobe connector at solenoid to monitor power while activating solenoid. The solenoid has power at all times and is activated by computer grounding white wire. Let me know how it goes, thanks
Customer: replied 1 year ago.
Sorry, my scan tool can't activate/deactivate vent solenoid which makes me wonder, why I have voltage at connector but it doesn't engage solenoid. Is it possible this is low amperage stray voltage that my meter is picking up but no amps to close the solenoid?
Expert:  Dan replied 1 year ago.
You can unplug the PCM and ground the white wire on pin 70 of connector 1 to activate solenoid. Or you can also backprobe white wire at connector and jump ground to it. But if solenoid is not being activated, there is no amperage going through it.
Customer: replied 1 year ago.
Where is the PCM module located on the HHR LT-2?
Expert:  Dan replied 1 year ago.
Here is a picture, it would probably be easier backprobing plug to ground it. With ECM unplugged your scan tool will not be able to communicate with it. Let me know if you have questions, thanks.
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https://www.dropbox.com/s/925q1ssui716pn8/pcmf.PNG?dl=0
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Customer: replied 1 year ago.
OK, so I can also check the red/white to frame ground to determine that B+ voltage is there and then run this B+ plus a separate frame ground to the vent solenoid to see if it closes?
Expert:  Dan replied 1 year ago.
Keep everything plugged in like it should be but have paperclips going into back side of connector so you can monitor power on red/white wire while grounding white wire. If power on white wire drops below 12v you know there is a connection problem. Let me know, thanks.
Customer: replied 1 year ago.
Do you know if the rear 2-pin chassis connector in the floor pan in back of the gas tank [that connects the to the red/white vent valve wire connector assembly] goes directly back to the fuse box under the hood or is there another connector/fuse box in-between?
Expert:  Dan replied 1 year ago.
No I do not have the connector diagram. I'd monitor power, if power drops then I'd run a new wire between fuse and solenoid assuming connectors look fine. Let me know how it goes, thanks.
Customer: replied 1 year ago.
I'll have to get back to you on this, Thanks
Expert:  Dan replied 1 year ago.
Sounds good, keep me updated. Thanks.
Customer: replied 1 year ago.
Still not enough voltage to close vent valve solenoid - Getting 11+ VDC at floor pan connector (right before the pigtail gaing to the Vent Valve Solenoid -This is a clean low mile, well maintained vehicle that shouldn't have any wiring issues, so is it possible that the ECM is responsible for "delivering" the lower voltage? If so can this be corrected by the Dealer "re-flashing" or would that mean a new ECM which is very $$$?
Expert:  Dan replied 1 year ago.
The voltage comes right from the fuse, the ecm has nothing to do with the voltage. You really need to monitor voltage while activating solenoid to see what type of voltage it holds under load. if it is dropping below 11v ever then you have a wiring/connection problem.
Customer: replied 1 year ago.
OK, but doesn't the ECM "ask" for a ground to be applied to close the valve (Valve is normally in the open position)? I guess the real question is this valve ALWAYS activated (held closed) by battery voltage unless the vehicle is turned off at which time it allows the vent to open, and that is the ONLY time when it is activate/deactivated?
Expert:  Dan replied 1 year ago.
The valve is always closed, the ECM provides the valve ground to open valve. It really sounds like a wiring problem still on positive wire if voltage has ever dropped below 11v but you will need to monitor power while activating valve to test.
Customer: replied 1 year ago.
I'm sure that you mean the opposite in that the valve is statically OPEN until a voltage is applied which is what I am finding with working on this issue. (In other words the vent solenoid part is in the open position right out of the box.
Expert:  Dan replied 1 year ago.
It is normally closed and opened when ECM grounds wire. This
Customer: replied 1 year ago.
Are you sure? because when I removed the original valve it was definitely in the OPEN position (I could easily blow air through it) and the replacement valve that I installed was exactly the same, so when current is applied, the valve CLOSES - same thing on the bench test when I applied 12VDC - it CLOSED the vent opening.
Customer: replied 1 year ago.
I assume that we are talking about the same vent valve at the REAR of the vehicle next to the canister & gas tank
Expert:  Dan replied 1 year ago.
I was thining purge valve for a minute which is a different valve, sorry about confusion. So this valve is normally open but code is still related to wiring and you still need to monitor power while activating valve.
Customer: replied 1 year ago.
Please confirm my last question so I understand how this circuit operates: 1) The vent valve solenoid is open with no voltage present when the car is turned off. 2) whenever the ignition is ON or RUN, then there is voltage applied to CLOSE the Vent Valve. Are there any other criteria when the ECM tells the Vent Valve to Open during the normal operation of the vehicle during low and high speed operation?
Expert:  Dan replied 1 year ago.
The vent solenoid gets voltage at all times and is open at all times. It closes when solenoid gets ground. The Vent valve purpose is mainly allow you to fuel tank properly. Let me know if you have questions, thanks.
Customer: replied 1 year ago.
Again, are talking about the same vent valve solenoid? Because if voltage is applied at all times then it is NOT open at all times, rather is CLOSED at all times - and only OPEN when car is off! Please clarify
Expert:  Dan replied 1 year ago.
The spring holds the valve open at all times and solenoid does get power at all times. The solenoid doesn't activate unless it gets ground from the ECM. When it activates, it closes.
Customer: replied 1 year ago.
I think that we're confusing what power to the solenoid means. To me, power to the solenoid means BOTH B+ and B- (a full 12VDC source to close the valve. But I what I believe you are saying is the solenoid gets ONLY B+ "Power" at all times and the B- is controlled by the ECM; therefore my question is under what conditions does the ECM provide this ground to CLOSE the solenoid valve?
Expert:  Dan replied 1 year ago.
Power would only mean B+ which is all that is required to provide 12v to valve. Once B- is applied to valve through ECM it completes the circuit activating the valve. The ECM should provide it ground when starting. I wanted to mention again if voltage ever dropped below 11v this points toward a wiring problem and I'd still start by monitoring B+ while activating solenoid.
Customer: replied 1 year ago.
OK, we're now on the same page for the meaning of "Power" as just B+ that clears up alot
So my original question above - when does the ECM provide the B- Ground? i.e. Ign on, Starting, running at idle, low speed, hiway speed or other conditions?
Expert:  Dan replied 1 year ago.
The ECM usually grounds the valve for a minute or so after starting to pressure test the system. If problem was anything other then wiring or valve it would set a different code. This code can only mean wiring, valve, or ECM which is very unlikely.