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thecardoc3, "A Mechanic's Life - Tales From Under the Hood" #664, 12 Dec 2012 8:13 am#MSG663
The author wonders if GM execs don't know or don't care and the answer is....both.
23 Telluride SX-P X-Line, 23 Camry XSE
The items besides the gas cap leaking that can cause codes are the purge valve and the vent valve along with some rubber tubing that carries the vacuum to the tank to do emissions checks.
The rubber parts deteriorate and crack causing a leak of the vacuum setting off certain codes. Heat above the engine aggravates the aging.
The purge valve may not be turning on to send vacuum to the charcoal cannister to let air flow through to remove gas vapors caught in it.
The vent valve may not be closing for the times when the emissions check verifies that there are no leaks in the tank, cap, tubing, etc., to allow the gas fumes to vent to atmosphere instead of being forced throught the charcoal canister where they will be caught by the carbon granules.
There also is a pressure sensor on top of the tank that measures the vacuum drawn on the tank/system by the purge valve and how quickly that vacuum deteriorates (measuring the leakage of air into the system).
Also note the relationship to the volume of fuel in the tank. The typical GM algorithm is to only run the leak tests when tank is between 15% and 80% or so in gasoline. Also the engine needs to be luke warm--not cold and not full normal temp. Try keeping your tank between 1/4 and 3/4 for a couple of weeks and lots of key starts. See if the light goes off because the system is able to correctly do several leak checks. The computer has to do a certain number of good tests before it will turn off the light.
Good luck.
2014 Malibu 2LT, 2015 Cruze 2LT,
My Ford Territory HAD the same problem now SOLVED. HOW ???
CHANGE both O2 Sensors.
Take out the Air Filter and give it a good clean with vaccume cleaner then put back in the car.
If this fails your Catalytic Converter is in need of replacement.
Change O2 sensors and ckean air filter first. Then take the car for good run up freeway. Your CEL shoukd stay off now.
MINE DID !!!!