how important is it?

[littlexj1]

that little air canister mounted behind the bumper on the passenger side?

[Hickey]

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[Matthew Currie]

Originally Posted by littlexj1

that little air canister mounted behind the bumper on the passenger side?

Depends a little on the year, and what you have for accessories. If it leaks, you lose various vacuum-operated functions: cruise control if you have it, front axle engagement if you have a disconnect axle, and heater control functions (heat will always default to defrost). If you simply bypass it, these things will work, but may stop working during low vacuum conditions, such as climbing a hill. This is just when you least want your 4WD to pop out, so if you have a front axle disconnect, fix the canister. On models with cruise control, the canister has two independent chambers, one for cruise and the other for axle and heater, so one side might be bad while the other isn't.