Crankshaft Position Sensor.

Well, is it or is it not your CPS sensor.   Jeep Part number 56027280

List US$86.70 but the "best price" should be  closer to US$72.00

Without going into the this sensors guts, let's just say it's a magnetic field sensor.  It contains a fairly strong magnet and spends it's life watching the flywheel.  The flywheel has several notches cut into it and as these pass the sensor it allows current to flow.

Generally this type of sensor never goes bad but...  It can suffer from a buildup of metal fragments and the wires will eventually suffer from engine heat.  If you pull your old CPS sensor and it is covered with metal fuzzies, wipe it off with a cloth and measure it again.  (Same goes for your ABS sensors)
On the 42RE transmission the CPS sensor connector looks like this and can be found back by the dipstick.


Using a DMM (Digital MultMeter) your going to probe Pins B and C. 
Watch the polarity, your Ohmmeter will have a RED and a BLACK lead
BLACK LEAD to RED LEAD to New Sensor Old Sensor
B C Infinite (OPEN) Infinite (OPEN)
C B 4.48 Mega Ohms 2.50 Mega Ohms

How do you get that thing out?  Well, this is where being a body builder isn't going to help.  If your forearms are fairly large you might have to drop the front shaft.  You get at the bolt that holds the sensor by using one swivel, and two 16" extensions.  The nut is 11mm.  Your going to run the shaft from just behind the cross member, up above the transmission linkage mounting bracket, add on the swivel, then run the second almost straight in on the nut.

Getting that sensor out isn't too hard but it helps if your a human pretzel.  Reach up in front of the transmission bell housing and grab it from the top.  You will need to take it out enough to turn the ear toward the engine bay, that allows the sensor to clear the firewall, and out it pops.

Sorta the reverse for installation.  My only real problem was getting the stupid bolt into the sensors hole.  And speaking of hole, This sensor has only one fixed hole setting the gap where the original might have an adjustable hole and relied on a paper spacer to attain the proper gap.  If this is your old sensor, now is the time to transfer a reference mark from the new one.

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