Expert: Roland Finston - 8/13/2011

Question
QUESTION: What is the module called which is next to the emissions control cannister. This is underneath the van, amidships, behind the engine. It's an electrical device (black plastic)with several tube connections (approx. 1/2") which connect to the cannister and elsewhere. I am getting a strong gaseous vapor coming from under the van at idle. Can't find any gas leaks.

ANSWER: Hi Jim,
It is probably the leak detection pump which is part of the emission vapor control system. There are many hoses involved in the vapor control system and probably one of them has a loose fitting. Let me know the year of your vehicle. You might also try to get a fault code by turning the ignition key:"on-off-on-off-on and leave on" doing that in 5 seconds or less elapsed time. Then see if the mileage reading on the odometer changes to show a 4-digit number preceded by a P. Or get a free code readout at a nationwide auto parts store such as Autozone. That might pinpoint where the leak is.
Roland

---------- FOLLOW-UP ----------

QUESTION: Thank you sir,
This is a 2005 Grand Caravan SXT, 3.8. I got these codes: p-0499 and p-0301. I replaced the electrical device(module)next to the cannister with no result. All nylon clamps were broken. Replaced them and I think everything is tight. I still have a strong gaseous vapor smell.

Answer
Hi Jim,
The 0499 code says that the circuit for the solenoid that controls the dumping of the vapor recover canister into the intake manifold is shorted to a higher than normal voltage level. That solenoid is said in the manual to be mounted on or near the right side of engine motor mount. It would have a hose(s) that connect to the canister. It has a 2-wire plug with colors dark blue/white and dark blue/brown and those wires connect directly to the 3rd plug of the powertrain control module (it is black with a natural color interior) on pins 20 and 20 respectively. So you would do well to inspect the harness wires and if nothing unusual is found then measure the continuity of each wire to its pins at the pcm plug, then check to see that neither wire is shorted to ground, and then check to see that neither wire show any voltage on it when the plugs at the ends are disconnected from the solenoid and from the pcm. That would be how I would approach this. It appears that the cannister is not being purged and thus the vapors, unless there is a hose leak in this system as well.
Roland