What you have is possibly a short-circuit issue. To answer your three questions.
#1. internally located in the transmission.
#2. Inside, you need to remove your transmission oil pan.
#3. ALL 99'-04' WJ USA built (export models excluded) with a 4.0L engine, have a 42RE transmission, regardless of what drive-train system you have, 2wd or 4wd/Awd.
00' WJ laredo L6/4.0L 242: stock (HIS)
96' ZJ limited V8/5.2L 249: stock (HERS)
94' ZJ laredo V8/5.2L 249: 2in BB Lift, 31"/BFG (HIS)
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Here for your OEM part # needs.
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WTB: ARB front bumper(ZJ) 12/7/13