How to get what your looking for on fixya...

Usually this just means the coolant temp sensor has failed. Without this input to the ECU I think it can cause engine shut down. It is possible to test this part with an ohm meter. Your shop manual should have a chart showing resistance at different temps.

You need to check and see what fault codes are in memory, there will be something there.

Could be something as simple as a dirty fuel filter.
Get a can of quick start at the store and have someone start it up, when it wants to die squirt a shot into the intake ... if it runs again for a bit you have a fuel delivery issue. Check the fuel pressure to see if the pump is functioning properly.

which engine? 2000 GC, is a body, stalling is and engine issues.

there are 5 reasons (physics) to stall, and 50 ways. (reality,say head valve stick hot only??? and lots more.)

ill not list them (searching shows my posts doings so 100 times)
but will ask you one questions.
can you save the stall with a fast right foot.??????????
ok 2 .
does the dash lamps (any ) go dead at stall point.?

the scan tool only works best , scanning and driving and for sure
at the stall point, so?
for example misfire codes clear in 1 second if gone.
so you missed that...... real time scanning is best, others like trips
to autozoned are near useless. IMO. why work, blind, ?

for better answers join a real jeep forum (google that)
this forum fxxxa , sux at this, it has NO structure here, nor abilities
to see your car, your engine, and others with issues related.
zippo here
join a real CG forum.

wow no year stated, nor engine size, you make this very hard.
stalls are complex.
how to cold engine? we cant guess that.
my wild guess. on why is here.
you need to watch engine RPM.
if rpm/s go too low below 800. say down to 500 that is a clue.
big clue. (means lack of engine power, or ISC is stuck closed or EGR main valve stuck open)
The ECU does every thing it can (ISC) to prevent stalls.
in fact as you select Drive or Reverse from park, the ECU adds throttle. (via is buddy ISC) the ISC adds air. and RPM rises.
The next question answer the reasons.
1: does a fast right foot, save the stall. yes or no?
easy, yes, hard, impossible no.??????????? a key test. and 100% free of charge. and tools. just a right foot.

Error, why not say what produced and error.
(my scan tool or my cluster display)
using a real scan tool youd get more errors, post the codes.
DO not decode them let us do that using the real FSM,

Rev. stall.
that means the ISC failed to add power
and on some engines, (MAF based) a vacuum leak will do that.
so will EGR stuck open (some engines have it ,others not)
what was RPM before you shift to reverse and did you
try to save it with a fast right foot.
there are lots more causes. up to 50.
(eg, leaking intake valves, sticking. on and on)
but first post the engine, ok.

we cant fix engine, with engine not stated, its not going to happen.
well,under 100 pages of tests. blind to engine.