Drivers side of the engine rear of the cylinder head a one wire connector to the sensor. Purple wire remove and ground to the engine aand the gauge should peg full hot. That will telll you gauge is good. Not bad to change usually <$10.
89 2.5 TBI, 4" RC lift, 1" Booms, SYE, Adams Driveshafts front and rear, Ford 8.8 with 4:88s, BFG 33X12.50X15, and a ton of other stuff.
AF Jeep Club Tail Number 184