H20 light on after filter change!?
 

WIF lamp 'Continuous ON', or intermittent and/or 'flickering' while driving?

When you changed the HFCM filter, did you drain the fuel out through the 3/4 round plug on the HFCM manifold (module front) first?

If the lamp is steady ON it could be that there's debris collected on the sensor pins or sediment build up in the reservoir that may not have come out with the drained off fuel.. It'll look like a clearish gel, or it may be shorted because of corrosion to the pins internal to the HFCM, or externally..

If you didn't drain the reservoir from the small plug, try that first and see if the WIF cancels.. If you did,, you might 'gently' remove the WIF sensor by turning it approx. 45 degrees CCW with a pair of pliers and pull it straight out.. Examine the sensor pins for any debis collected, then use a flashlight and look into the reservoir through the sensor hole for any acumulated trash that may be shorting the sensor.. It may have shown up on the drain plug, or visable through the drain hole as well..

Driving with the WIF lamp on won't cause any issues, unless there is 'actually' water in the system, especially a large amout.. When you drain the HFCM it's always a good practice to capture/sample the drained the fuel for any water, with or without an active lamp..

Also,, a trick drain option for the HFCM is using the LFC (Low Cab Forward) truck module drain plug.. It's a 'thumbscrew' type replacement that you can either hand tighten, use pliers on, and has the standard hex as well to use a allen wrench/driver on.. The great part about using this plug, is it's easy to remove, it has a fish hook T-type end that allows the plug to drop out a tad and 'wicks' the fuel on down and away from the HFCM keeping it from running down the frame, and of course down your arm and dripping off your elbow :)

Here's an image of the LCF drain along side the OEM plug.... Part # 6E7Z-9C082-A