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Roy Belding
Roy Belding, ASE Certified Technician
Category: Buick
Satisfied Customers: 6049
Experience:  Master ASE since 1980
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Buick Rendezvous: 2004 Buick Rendezvous, service engine light

Customer Question

2004 Buick Rendezvous, service engine light brought up a Po449 code which we replaced vent valve solenoid. Light did not go away. Took it to a mechanic and he said the same thing, even though that part was replaced but code also brought up harness and they said dealer told them they discontinued harnesses. My car need to pass emissions last week...I am lost
Submitted: 2 years ago.
Category: Buick
Expert:  Roy Belding replied 2 years ago.
good afternoon my name is ***** ***** I will assist.
codes identify a system not working. it never tells you a part has failed.
if there is a harness problem, your mechanic needs to find the failure and repair it. if he cannot then you need to go to another shop.
the vent valve needs 12 volts to the solenoid. the other wire is the ground which is controlled by the pcm. when the evap system tests itself, it grounds the wire or closes the vent to allow the test for any leaks in the system.
you need to check to be sure there is no leaks, voltage is supplied as needed and see if the pcm is closing the vent when required. you need a scan tool to activate the solenoid and monitor its actions. you can run a bay test to be sure the system will pass when the actual test is performed. if it fails then you would at least know that there is still an existing issue and what area is failing. then you go after that failure.