Do you have a check engine light or any trouble codes? Specifically any P0440-P0449 or P0450-P0459 codes? That hose should go to the vapor canister. There should be two U-shaped hoses on the vapor canister, a large one and a small one. The small one should connect to this (pictured) hose, and on the engine end it should be connected to the canister purge valve, mounted next to the battery. The larger hose should connect to the leak detection pump which is hidden beneath the Main Distribution Panel. Someone may have replaced/installed another hose because they found this one bad. But if that is not the case, and this hose is disconnected, you should have trouble codes.
. No codes at all. Only issue with this truck is the loss of acceleration going up hill. And little take off power. Since bought I have replaced the tps, map, new plugs , pcv and crank case breather valve,, wires, cap, rotor. Removed the cat ( no emmisions here), replacing muffler next.. has small exhaust leak, not a big issue. and still having issue.. somone suggested fuel pump assembly.. so idk. Anyway, back to the hose. Just happened to see this sitting there and plugged on both ends. Looked through everything and nothing is missing a hose. Was wondering if someone had removed something completely, or we're a hose for diff motor. I will double check everything else though.
After looking again the cover has both its hoses hooked up properly.
The other hose pictured goes straight down and is attached to the frame. And sits next to the evap canister under the frame. With no obvious place to connect it to. Never seen an extra hose just sitting around some where. But who knows.
The picture of the capped hose by by the P/S pump, is a front differential vent hose for 4WD trucks. The other end should be attached to the front axle tube if it's a 4WD. If it's 2WD, it was probably a factory mistake. My 98 Cherokee has the same vent hose. They place it high like that so water doesn't get in the axle when crossing streams & such.