2004 Pontiac Grand Am fuel EVAP system

TTOOMMYY40

MEMBER
2004 PONTIAC GRAND AM
6 CYL
FWD
AUTOMATIC
156,000 MILES

Check engine light blazing had the codes run and came up with a 446 evap system performance code. I replaced the vent valve and reset the computer, the light stayed off several days and came back on again. I have checked for vacum leaks and cannot find oneand its the same code again could the vapor cannister need be replaced, help

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BLACKOP555

MECHANIC
10,371 POSTS

Can you post back the exact code in P***** format. I will be able to help you fully then.

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Tuesday, June 1st, 2010 AT 10:44 AM

TTOOMMYY40

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The code is po446 vent system performance according to the repair manual

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Tuesday, June 1st, 2010 AT 7:48 PM

BLACKOP555

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Alright. First check the condition of the wiring harness on your vent solenoid. Make sure its getting its full 12v.

Next I woudl check the gascap make sure its seals are all in it and its not leaking. Taht will throw that code

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Wednesday, June 2nd, 2010 AT 9:47 AM

TTOOMMYY40

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Ive replaced the gas cap and the wiring harness is in good shape but ive not checked the voltage also strangly my brake pedel is not as soft as it was before the service engine soon light went off. And my fuel milage has increased dramatically from 300 to a tank of gas to almost 400 to a tank maybe that info may give you better insight, thanks

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Wednesday, June 2nd, 2010 AT 8:49 PM

BLACKOP555

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I cant see how the pedal would be related. And the gas mileage WOW theres a rare possibility they are related but I doubt that.

This code is set when theres a issue found in the control circuit so since you replaced the vent and the harness it sounds like its a issue with the pcm but you dont wanna throw a new one at it and it not be that.

Where did the replacement harness connect at on the vent valve? Id check the wiring from the vent valve all the way back to the computer for internal damage. Best way is to take them off and perform voltage drop tests on it because you could have just one strand in there suppling 12v and ground but not carry enough current to do anything