Purchased a 2004 Caravan in December and had an issue with the MIL coming on sometime in April. Had it tested and it came back as EVAP (not sure which exact EVAP code). Tried a 3rd part gas cap which did no good then finally put a Dodge cap on, reset the light (disconnected the battery) and all was well until last week when the MIL came back on. Had it tested and it's EVAP again. The mechanic reset it, but it came back on after a couple of days.

Now, I don't mind putting a gas cap on the van every 6 months or so, but what else could the issue be? Especially since a new cap solved it for as long as it did?

 

Check all of the fuel vapor hoses from the canister in front of the gas tank to the purge solenoid mounted near the RH headlamp. The rubber hoses may be cracked someplace, also behind and underneath the air cleaner.

 

I can't see a gas cap fixing it for only a few months at a time. Caravans are notorius for the Leak Detection Pumps going bad and cracked hoses. Remove the air cleaner box with one 10mm bolt and pull up to release the grommet. Follow the 2 lines off of the purge solenoid and see if it is cracked after the 90 degree bend or at the service port. If it's good there you need to look at the hoses from the Leak Detection Pump (NVLD solenoid) to the canister. If that's not it, you need to have it checked out for a LDP, a tank or a purge solenoid.

 

Well, my CEL has been on for 6 months for the same thing. Mine says large evap leak. I can't find it either. It used to reset just fine by disconnecting the battery, but that doesn't work anymore. It doesn't seem to affect the driving, so I haven't tried all that hard to fix it. Let me know what you find.

 

I had the same problem. The issue was inside of the LDP vent valve, located on the underside of the van (directly below driver's seat.) The codes would return even after it was reset. Eventually, a whistling noise developed from a pinhole leak in the diaphram. This helped me locate the source. The noise didn't develop for several weeks though. Just a suggestion if no obvious source.

 

I just purchased a used 2004 GC with 40,000 miles. Very nice vehicle, but the MIL was on indicating a P0440 code. The Dodge service dept. diag'd it and said it was a bad NVLD pump along with a vapor canister that needs to be replaced. They're in the process of making the repair now. Total to repair is $509. Will let you know if that does the trick.