which of 3 engine do you have, gas or diesel and what size?
Are battery terminals clean????????????
Ill assume yes.
below will be 4.0L answers ,gas.
id say lost 12vdc power to EFI system and cluster.
the cluster dropping is lost power.
the cluster is computer in its own right.
and has 2 power pins, one is power to run, and power memory.
can be simple as a loose fuse.
to find it i inspect first. (im retired ET and can find them all)
if you had used a scan tool ($10) it would tell you why.
for example see all sensors go dead.
or the scan tool drops comms mind scan, lost DC POWER>
the scan tool will also tell you if the ASD relay drops and WHY!!!
if 12vdc did not die, first.
i start at the battery, after al batteries are weak technology, (acid/lead) some only last 3 years, (weak tech)
battery lugs corroded (at 4 ends)
2 cables 4 ends.
the hard part, (only) is the intermittancy.
cant fix working perfect cars, can not.
might be a loose fuse?
to isolate the true cause next time have all things ON , in car
head lights, HVAC blower on max. radio. all things.
now what dies????? a big big clue that.......!!!!
the power system is like a tree.
what branch is dead, puts us on track.
04 WJ jeep , i have the full factory FSM
can take you to the spot it fails.
lets say cluster power pin C1p7 drops dead (02 fsm names)
that means power from JB fuse 22 dropped. JB is cab box.
or its bad, (hair cracks in fuse, loose, or rusty) try a new fuse.?
or Fus22
it's input died, and that his the key switch bad, or before it.
called ST Run 21 (fsm)
see photos below for St run 21 feed, sources.
the PDC fuse top seen here, is PDC fuse F8 (engine bay)
if that top path is good, the the key switch is bad.
end story.
finding it, i use a logging voltmeter,
in the olden days, id have an analog meter sitting on passengers
seat, and at stall glance over, and go, gee, the F8 feed is good
so move my test wire to ST21 side, see it die or not.
walking the test wire from top of below to the cluster.
battery is top. last item below is cluster,
this is the fail path.
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