PontiacBonnevilleClub.com

I drive an 01 Bonneville, and for a long time my service engine soon light has been on. It has been throwing the PO442 code a lot. I have already replaced the gas cap, and I took the car to a mechanic a few days ago. When he scanned the car, a PO440 code popped up and he replaced the vapor canister after he checked the hoses for leaks (which were all okay). He said when he took the hoses off of the vapor canister, liquid fuel came out, and the canister was plugged. I scanned the car about an hour ago and got the code PO442. What could be setting the light off?

The shop manual goes through an entire diagnostic process that involves checking for leaks, checking the EVAP purge solenoid valve, introducing smoke into the system with a special tool and looking for a leak with a special white light to find small leaks that otherwise would not be detected, testing other components such as the fuel tank pressure sensor and the EVAP canister vent solenoid valve. Perhaps you can replace the EVAP purge solenoid and see if that clears it.

I'm having VERY similar troubles with mine.... replaced both the purge and the canister. Keeps alternating throwing codes for both, as well as general evap. How is your fuel filler neck? Mines rusted to crap and my theory is is not getting a proper seal and possibly has small holes/cracks caused by rust which is causing the codes and the ses.

When they replaced the canister did they replace the evap vent valve?

isnt the vent valve the same thing as the canister? I replaced the canister under the back wheel well and then a week later the code popped on for the purge valve on the front top of the engine.