If it's like my 2001, it's in the driver's side front fender well, under the air cleaner. Here's a diagram:
The intake apparently sucks in water, which pools inside the rubber cover of the pump's motor, eventually corroding out the motor.
The solution is to remove the pump and replace it with a new one, but drill a 1/4" hole in the middle of the rubber cover, so any ingested water will drain harmlessly out. Also, reroute the intake so it sticks UP instead of DOWN. After replacing mine, it looks like this:
While I was in there, I also replaced the relay to the pump, and for good measure, I replaced the Check Valve, which plumbs into the exhaust manifold in the back of the engine, centered right in front of the firewall. Mine had also *melted* the 30-amp fuse in the under-hood fuse box, so I replaced the entire fuse box with one sourced from a salvage yard.
Here's the steps to replace the pump:
Raise the vehicle.
Remove driver's side front wheel.
Remove the fasteners from the front portion of the left front wheel well/splash shield.
Reposition the splash shield to gain access to the pump and bracket assembly.
Reposition the sound insulator to gain access to the pump and bracket assembly.
Disconnect the pump electrical connector.
Remove the pump/bracket assembly fasteners.
Reposition the pump and bracket assembly to gain access to the outlet hose.
Remove the outlet hose from the pump.
Remove the pump and bracket assembly from the vehicle.
Because emissions controls that are part of the exhaust can affect one another, I'd also recommend pulling off your EGR valve and cleaning the pintle and make sure you can push it in, and that it springs back out. Also, for good measure, check your PCV valve to see if it's clogged or in my case, it was *missing*.
I don't know if the check valve can be tested or not, but since I'd replaced the secondary AIR pump, its relay, and the fuse box, I decided it was easier to replace the one remaining component in that system than to risk trusting it.
