I replaced the air-actuated front diff on my 2003 XL7 with a plain old diff from a 97 Sidekick. I'm putting on an aftermarket front bumper so I'm looking to toss the air pump which is mounted to the backside of the original bumper; no sense in having it there if it's not actually doing anything. How do you rig it up so the 4wd light still comes on when shifting into 4wd after the pump has been removed?

You can wire the transfer case switch directly to the light - going from memory - one wire is black/orange and the other is orange/black.

I mounted to the beside the rad and plugged the hose so when I switch into 4x it comes on

You can wire the transfer case switch directly to the light - going from memory - one wire is black/orange and the other is orange/black.

Does that mean I have to take the dash apart or  just hook it to the wires coming out of the air pump? I'm not familiar with the wiring setup on these.

I am not really interested in relocating the air pump, it's just another item adding clutter to an already crowded engine compartment. I'd much rather just get rid of it even if it's a bit more work to figure out the wires.

There are a couple of different ways to do it ...

My car is one of the early ones with a separate 4WD controller in the driver's side foot well - that would be the easiest place for me - easiest to not get into trouble, but it'll take some degree of twist & contortion. 

Later models, and I suspect yours will be one of them, have the controller integrated into the ECM/PCM and I would not want to be cutting & splicing wires near that - too easy to get confused - the dash is not that hard to pull, and if I were doing it on a later model, I would probably pull the dash, splice a wire into the dash harness and then fish that through and connect it to the transfer case switch.

I just had a look at the XL-7 wiring diagram and confirmed the black/orange & orange/black wire colors - BUT - there are multiple separate circuits using those colors at the PCM confirming that it's not a good idea to poke around there.

On second thoughts - on the later models - the easiest way is to jumper the red wire to the pink wire at the air pump connector.

I mounted to the beside the rad and plugged the hose so when I switch into 4x it comes on

I did the same, it takes literally 1 minute and the appropriate sensors/lights work as they should when shifted in 4wd. No messing with wiring. A gold tee and some epoxy and you're good to go.

On second thoughts - on the later models - the easiest way is to jumper the red wire to the pink wire at the air pump connector

I tried this first as it was easiest to quickly check. Placing a jumper between red and pink results in the 4wd light illuminated all the time, even in 2wd.

Try adding a resistor from the red/pink jumper to ground - the black wire - something like a 10k resistor should do it.

Thanks fordem, I wired a 10k resistor between ground and the jumper wire and everything works as it should!

You're welcome...