P0496 code 2005 Chevy trailblazer

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coolcj56
Posts: 4
Joined: Sat Jan 28, 2017 12:12 pm
Vehicle: 2005 chevy trailblazer 4.2L

P0496 code 2005 Chevy trailblazer

Postby coolcj56 » Sat Jan 28, 2017 12:24 pm

ok so my light came on...0496 was determined, replaced purge valve. turned light out...after a while came back on, replaced gas cap, same thing, vent valve, same thing, map sensor, same thing, fuel pressure sensor, same thing... smoke tested..passed... now I drive it for a while and the light turned out by it self but after like 4 cold start-ups It comes back on, so far it did that twice in the past 2-3 months now its back on...idk what to do thinking about replacing carbon canister and MAF sensor next.....I need help...


kev2
Posts: 6522
Joined: Sat Aug 29, 2009 4:24 pm

Re: P0496 code 2005 Chevy trailblazer

Postby kev2 » Sun Jan 29, 2017 12:29 pm

Why would you think MAF and MAP - Are there more codes?

the test does not run all the time so several days may pass till next test.
Check the purge valve for sealing, you can use a vac gauge on EVAP side of valve.


My thoughts -
Sometimes overfilling fuel tank after click off will degrade screen and allow carbon to obstruct purge seating... could remove valve and look for evidence. A scanner could be used to command system on and observe TPS (tank Sensor) change while vac cking at purge, confirm it will close and open vacuum.

coolcj56
Posts: 4
Joined: Sat Jan 28, 2017 12:12 pm
Vehicle: 2005 chevy trailblazer 4.2L

Re: P0496 code 2005 Chevy trailblazer

Postby coolcj56 » Sun Jan 29, 2017 12:40 pm

no other codes..just guessing as to what it could be...and yeah everytime i fill my tank i like to overfill..but i replace purge valve and vent valve and FPS....i was researching and i was thinking from what i saw..like what its just the hoses...can they were not cleaned before replacement of parts...and car does drive alot on E so dust and everything is probably clogging the hoses???

kev2
Posts: 6522
Joined: Sat Aug 29, 2009 4:24 pm

Re: P0496 code 2005 Chevy trailblazer

Postby kev2 » Sun Jan 29, 2017 1:09 pm

not clogging hoses but accumulating on valves of the purge and vent - purge more likely as vacuum draws any particles that way... preventing from sealing...

Maybe check the canister to purge vac line at the canister for particles before replacing.
definitely remove and check purge new is not a guaranty of good esp if aftermarket.

Professional thinking is refuel @ 1/8 minimum with 1/4 being the goal.

coolcj56
Posts: 4
Joined: Sat Jan 28, 2017 12:12 pm
Vehicle: 2005 chevy trailblazer 4.2L

Re: P0496 code 2005 Chevy trailblazer

Postby coolcj56 » Tue Jan 31, 2017 8:22 pm

update so after alll the money i put into this vehicle for emissions alone...i finally found out that the hose from the breather i think came off and the new duralast purge vavle i put n was no good....so put factory el delco
purge valve on there and cleaned all hoses just cause....got oil changed, and tune up today so i pretty confident that the light will not come back on for the same code...


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