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Old 11-17-2012, 04:00 PM   #1
Bennie77
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Default Code PO 496 (Evap system)

Been getting this code a few times lately. Evap flow during a non purge condition. Any help would be appreciated.
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Old 11-17-2012, 04:16 PM   #2
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Check your gas cap. Untighten it and then tighten it back hearing the clicks several times. With the weather changing from warm to cold this is usually when gas caps get loose.

If your code doesnt go away check back in here...
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Old 11-17-2012, 04:52 PM   #3
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Will do. Thanks.
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Old 11-17-2012, 09:14 PM   #4
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Well, I removed the neg battery cable to clear the code, tightened gas cap but the check engine light came on again.
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Old 11-17-2012, 10:32 PM   #5
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purge valve stuck open?
Disconnect it and blow through it. you should not be able to.
You can also connect a 12vdc source to it and verify it opens.
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Old 11-17-2012, 10:32 PM   #6
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My read is saying, that the EVAP system is seeing a higher vacuum in the system, than it should. If the purge solenoid valve does not shutoff correctly, the intake manifold will keep adding vacuum to the fuel tank to the point that it exceeds the desired level, an will trip that fault code.
That purge solenoid valve sounds like its starting to fail. Its located just forward of the oil fill spout. If everything looks good from the outside (electrical connection and plumbing etc), maybe you could rap on it a little, to see if might temporarily correct itself. If so, you would then know what to buy, unless this is still covered by GM.
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Old 11-19-2012, 06:14 PM   #7
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Quote:
Originally Posted by GOPHERIT View Post
My read is saying, that the EVAP system is seeing a higher vacuum in the system, than it should. If the purge solenoid valve does not shutoff correctly, the intake manifold will keep adding vacuum to the fuel tank to the point that it exceeds the desired level, an will trip that fault code.
That purge solenoid valve sounds like its starting to fail. Its located just forward of the oil fill spout. If everything looks good from the outside (electrical connection and plumbing etc), maybe you could rap on it a little, to see if might temporarily correct itself. If so, you would then know what to buy, unless this is still covered by GM.
I am not sure what I am looking for. Does someone have a diagram showing the part?

Thanks
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Old 11-19-2012, 06:34 PM   #8
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^^^^ I don't, but you couldn't ask for an easier part to get to and see. Remove your engine cover (if its still on), lift up the 2 heater hoses just a touch, where they pass by the front of the passenger side valve cover. There you will see a black plastic module about 2x2 in size. A vac line in and out, plus an elect connector attached to it. That *is* the purge valve.
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Old 11-19-2012, 08:10 PM   #9
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I appreciate all the help, but at the risk of sounding stupid, I am confused. One says in front of oil fill on drivers side, the other in front of valve cover on Passenger side. I am stumped.
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Old 11-19-2012, 08:49 PM   #10
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^^^ Well I checked my post #6, to see if I goofed, but it only says *oil spout*. I don't know where the *drivers side info is coming from.


Added info---- I'm talking about this under the assumption that your car is indeed a V8. The fault, and cause is the same for a V6, but the valve is in a different location.

Last edited by GOPHERIT; 11-19-2012 at 09:32 PM. Reason: added info
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Old 11-19-2012, 10:58 PM   #11
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Bennie, do a google image search for purge solenoid or purge valve on the G8. you will see what it should look like. It is an easy check.
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Old 11-20-2012, 01:18 AM   #12
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Make sure there are no cracks in the gas cap. The evap code is almost always the cap. Its an emission code so the battery disconnect doesn't always work.
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Old 11-20-2012, 02:54 AM   #13
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Quote:
Originally Posted by GOPHERIT View Post
^^^ Well I checked my post #6, to see if I goofed, but it only says *oil spout*. I don't know where the *drivers side info is coming from.


Added info---- I'm talking about this under the assumption that your car is indeed a V8. The fault, and cause is the same for a V6, but the valve is in a different location.
No. I have a V6! Oil spout is on drivers side. I am in V6 tech forum, correct?
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Old 11-20-2012, 11:13 AM   #14
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Bennie77, you are in the correct posting location. I have a habit of reading the thread, without verifying what section it is located in (my bad). If I read the diagrams correctly, the purge valve is located just above a couple of the spark plug coils, on the passenger side. It looks to be a cylindrical shape with a vac line at each end of it.
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Old 11-21-2012, 01:48 AM   #15
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Quote:
Originally Posted by JESUSFREAK702 View Post
Make sure there are no cracks in the gas cap. The evap code is almost always the cap. Its an emission code so the battery disconnect doesn't always work.
p0455 is the cap code.
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Old 11-21-2012, 03:42 AM   #16
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Quote:
Originally Posted by todds87ss View Post
p0455 is the cap code.
I humbly stand corrected.

http://www.obd-codes.com/p0496
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Old 11-21-2012, 07:54 AM   #17
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Replace the EVAP purge solenoid. P0496 is EVAP purge during non-flow operation, which means the system is seeing vaccum while the system is being commanded sealed. this is caused by a purge solenoid being stuck open. part is $50 and is located on the pass side close to the intake manifold near the cowl... p0455 is EVAP large leak usually a cap left completely off or a EVAP vent valve stuck open.. P0442 is a EVAP small leak, usually a gas cap.... hope this helps
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Old 11-21-2012, 08:15 AM   #18
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Well, I did check the gas cap previously. It looked fine. Anyway, got gas last night, and after filling up, the cel is no longer coming on. Coincidence? Maybe. I will keep an eye on it, and if the code returns, will look into the evap purge valve. Thank you all for your help!
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Old 12-06-2012, 09:19 AM   #19
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Well, the cel has come on intermittantly so I got a new purge valve. Now, any tips on getting the connectors off? Don't want to break anything. I was able to disconnect the electrical connector, but not sure how the others come off.
Thanks
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Old 12-06-2012, 12:53 PM   #20
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Wouldn't you know, they can't make it easy. They show you need a removal tool (the tool in the GM service manual is P/N EN-46843) It looks like a device that would slip around the pipe coming out of the valve an under the hose locking collar attached to it. It probably probably forces a locking ring outboard, so you could then pull the hose away from the valve over the raised retaining lip on the pipe. There might be an after market vendor that sells a tool, that will do what is needed here, say from an auto parts store. Might be a tough find. If a lot of GM cars use this same type of disconnect technique, maybe finding a tool won't be that hard.
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