Where is the air leak detection pump located on my van.

not sure on this one but sometimes you can trace the vacuum hose to the charcoal canister and the LDP is generally near it. The pump should have at least two large hoses (about 3/4 inside dia.) One of them will go to the charcoal canister and the other will probably be routed to the frame in the vicinity because this one is merely vented to atmosphere (except when the computer commands it to close) so the tank will not build pressure. One of the most common cause for an LDP trouble code is related to a restricted vent hose due to debris. could be a spider.