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jim, ASE Certified Technician
Category: Pontiac
Satisfied Customers: 1317
Experience:  ASE Certified in A6,A8,L1, Plus California Licensed Smog Technician
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Pontiac G5: Hi there, I have a 2007 Pontiac G5 and my Check

Customer Question

Hi there,
I have a 2007 Pontiac G5 and my Check Engine light likes to be on; the error says something about the Emissions or Ventilatoins in the fuel system.
I assume that to be the fuel ventilation in the back/underneath the car. So I got it nice and cleaned out today, cleared the warning, and within 30 minutes of run time, that engine light was back on again. I'm assuming it's still the same problem but haven't gone back to check that out yes.
Advice would be much appreciated! Thanks!
Submitted: 5 years ago.
Category: Pontiac
Expert:  jim replied 5 years ago.
When the check engine light comes on it will store a code in memory related to the problem. You need to retrieve this code and send it to me and we can isolate the problem down from there. Some auto part stores like Auto Zone or some repair shops will retrieve this codes for free.
Customer: replied 5 years ago.
Hi there; here is the code and description:
P0496 - Evaporative Emission System - High Purge Flow.

I have taken the fuel vent system (box by the rear axle) off and opened the filter and blew (Air Compressor) out as much dust/dirt as I could, including the sponge.
I blew through the hoses a little bit too. I cleared the alarm but like I said, it was back on again within 30 minutes of run-time. (Same alarm)
I refueled just now; before the valve would kick out every few seconds because the gas couldn't drain fast enough (which happens if the vent is clogged) and that was pretty good now. I could fill gas at full speed for 35 Liters before it kicked out first time. (Usually it was 7-8 Liters)
Do you need any other information?
Expert:  jim replied 5 years ago.

The next step is to do the following test.

1. Disconnect the electrical connector from the purge solenoid.

2. Disconnect the vapor line that goes to the charcoal canister from the purge solenoid.

3. Start the engine.

4. Test for vacuum on the open port on the purge solenoid. There should be no vacuum.

5. If vacuum is detected, the purge solenoid is defective.

Customer: replied 5 years ago.
Hey sir, I've been ridiculously busy with emergency duff and a funeral and so that's why I ignored this for a while. I haven't had time to try your suggestion yet. I really hope I'll be able to try it on Saturday. I'll keep you posted.
Expert:  jim replied 5 years ago.
Hope everything is well and contact me when you can. thanx for the update.
Customer: replied 5 years ago.
Good afternoon,
I just got in from trying your suggestion. I think I tried what you suggested; there was no vacuum. So I assume that means that the solenoid is ok?
Is there something else I can try?
Expert:  jim replied 5 years ago.
The purge solenoid is mounted on the engine near the oil filler cap. It has a Pink and Black wire and a Dark Green and White wire.
Is this the solenoid you checked?
Customer: replied 5 years ago.
No, that is definitely not what I checked! :( Let me go out right now and check that!
I'll let you know.
Expert:  jim replied 5 years ago.


Customer: replied 5 years ago.
Ok I think I checked the right hose. The one appeared to me to go into the engine (opposite side from the electrical connector) and so I I disconnected the one going back somewhere (Same side as electrical connector. Was that the right one?
I don't know how much vacuum you were expecting but I couldn't feel any vacuum with my fingers. I tried holding a small piece of plastic to it and it didn't seem to suck to it at all.
Expert:  jim replied 5 years ago.


Number 11 is the line to disconnect from the solenoid, you will no this is the one because you will see a service port with a green cap on that line. Then you will be checking for vacuum on the solenoid it self with the engine running and the electrical connector on the solenoid unplugged. If there is vacuum you will feel it there with your finger. It will try to suck your finger into the solenoid (it can't) but you feel suction there.

Customer: replied 5 years ago.
I don't know anything about a service port with a green cap; but the one line goes into the engine; I changed the other one, the one that goes back to the rear end of the car.
I followed your instructions and there is no vacuum.
Any other suggestions?
Expert:  jim replied 5 years ago.
The PO496 tests for undesired intake manifold vacuum flow to the evaporative emission (EVAP) system. The control module seals the EVAP system by commanding the EVAP canister purge solenoid valve OFF and the EVAP canister vent solenoid valve ON. At this point you would need to have the vehicle hooked up to a scanner that has the correct software, to make sure this is happening. 90% percent of the problems we see with this code is a faulty purge control solenoid, the other 10% we see both the purge and vent solenoids are bad.
Customer: replied 5 years ago.
Last fall I had the same error code, and then that time I just cleaned out the fuel ventilation box that's on/near the rear axle - where that sponge is inside and had gotten clogged with dirt. I just cleaned it and cleared the error and then it was good until a few weeks ago.
I thought it was the same thing again but this time when I cleaned and cleared, the light came back on again after about 20 minutes of driving.

I'm not sure but is the "vent solenoid" you mentioned have anything to do with that vent that I was talking about?
Thanks for your help!
Expert:  jim replied 5 years ago.

The vent solenoid is at the rear.graphic


1 - Fuel Tank
2 - Fuel Pump and Sender Assembly
3 - Fuel Tank Pressure Sensor
4 - Evaporative Emission (EVAP) Canister Vent Solenoid Valve
5 - Evaporative Emission (EVAP) Canister

jim and 3 other Pontiac Specialists are ready to help you
Customer: replied 5 years ago.
I there, thanks for your help! I haven't tried your last suggestion yet, I hope I can soon but I'll accept that answer already so you get your money.
Can i still ask questions (If I have any) after I "accept" your answer?
Expert:  jim replied 5 years ago.
You can post to this question anytime and I will get back to you.
Customer: replied 5 years ago.
Hi there - I need to get this thing wrapped up because I'm leaving for a 6 week trip on Sunday. :)

Ok, I'm not even going to try to pretend to know anything; i need to know if I even know what I'm doing. :)
I believe the canister is that 'box' approximately 12"x10"x4" or something like so. It is located on/close to the rear axle of the car; it has two hoses close together going into the bottom, and one hose going into the top of so-called canister. The three said hoses are all on the same side of the canister.
Make sense?
There are two electrical connections to the canister, one towards the bottom and would appear to be connected with something (sensor??) in relation to the two hoses going into the bottom of the canister.
The other electrical connector is close to the top where the single hose comes in. (Vent Solenoid?)
The top bracket where the hose mounts to, I can snap off and open up and take a sponge out that I can - and have - cleaned out. Is that what they call the "Vent Solenoid"?
Anyway, to that top electrical connector, I attached power to and the solenoid "jumped". It was definitely alive. Come to think, I think I ended up forgetting to see if I could blow through it - but something obviously moved inside, you could hear it and feel it jerk a little.
The other bracket where the other two hoses are attached appears to be non-removable.
Somebody suggested I had a leak in the line. I don't know, but I do know that after cleaning out the sponge and area, I can go and refuel much faster. But after about a month, the fuel drains into the tank so slow the nozzle keeps kicking out when re-fueling.
It astonishes me that it would have to be cleaned every month.. ??? How can so much dust get in there?
Would you suggest I buy a new canister with everything? Or is there something else to try?
Am I even close to doing what you had in mind? :| I've already learned a lot and I'm glad for anything I can learn.
thanks for your patient help! :)
Expert:  jim replied 5 years ago.

The vent solenoid is at the back, when you energized it. The solenoid should click normally and a vacuum pump should hold vacuum at the port of the solenoid. If it doesn't hold vacuum the solenoid is bad.