Got a 98 isuzu hombre space cab 4.3 L V6 4x4 manual transmission. Back up lights will not work. Changed bulbs checked fuses (both under hood) and even changed back up switch/sensor on side of gear box.. Seems to be a short somewhere.. Any quick fixes or suggestions that I might have missed?

the 4cy. or the v6 (4,x,V)
there are plugs, wrong plugs, or
gaped wrong, and new plugs can be bad, I have a nice collection of new mutant spark plugs. on the wall.
wires bad. whey you replace spark plugs
the wires break so put new NGK wire on it , mag wire are best.
or you mixed the wire order.
do not mix the HV wire( the large high voltage wire)
that apples to both distriubors and the 4 cylinder 2.2L with 2 coil packs
the V6 has one coil pack
the gap is .045 v6 and spark gap 2.2 is .040"

Check for power at connection

breaks = brakes?
the brakes use vacuum but never changes it.
so...... if it does, the booster diaphram is cracked.
OD, can be just a bad OD. switch or more complex.
did you scan the TCM yet if it has one?

why state vacuum high, then not state the values seen?
you connect the gauge, and it reads what? 19inches HG at hot idle is common.
or 0.64 bar (outside usa you use BAR) as you said pressure word for vacuum and is ok in pure science that word) but make me think yoiu are not in USA? or Canada maybe....????

i bet vacuum is just ok.
the issues are with the transmission and its controls.
post is older, are you still having issues.
do say and we can link you up to FSM information on 0D.
the book covers this.... ever see a real FSM before.
the real factory service manual,, (buy one, and win?)
or if in USA , alldata.com is #1 online version of same.....
there are others, but nobody ever posts the country
making most answers wrong, including MINE.

i only have questions, after all im blind cant see car nor open hood.
so... what engine is there, transmissions match engines. so....

omg its really a chebby. Chevy
The pickup was also sold by Isuzu as the Hombre from 1996 through 2000, but only in North America
its not ISUZU at all.
you should know this and post to chevy, S10
2.2 liter or 4.3L engine
my guess is 4.3L with Brazil front sheet metal.

there are 12 control lines from the PCM puter,
and the transmission,
to find out why the OD fails
we first check all fuse..... (on all electric fails we do that)
then check levels hot, by the BOOK.
then scan the PCM for transmission errors, P07xx ? codes>

i look at the alldata. com at the Hombre 98 , pcm page.
schematics.
od .
we make sure no errors from PCM
then check the switch, to PCM for OD active.
if the input is ok.
then we check the solenoid voltages in OD.
if correct then the problem is ok, outside trans, and not inside.

This trans is electronically shifted.
and uses a computer (TCM)
so inputs must be right to TCM
an outputs correct. if not , never blame the tranny first.

will be one of these really need a pic. https://www.carid.com/1998-isuzu-hombre-fuel-delivery-parts/

I haven't worked on an escape, but i can tell you that switch is on the transmission.

There is a small fuse in the cab fuse block ,for the insterment panel that is verry easy to miss if you don,t look close ,it is hidden kind of at the top of the fuse block behind the wires,

There is a way to bypass the 98 Hombre.... Go to this link. Its under PERMANENT FIX

http://vatspasslockpasskeysecurityhelp.yolasite.com/

Please check the cables lead to your rear turn lamp for loose connection. Both turning lamps ( rear and front) should work to keep turning lights back to normal blink.
Regards

4 wheel drive?, size motor? have you probed all the fuses under hood and dash? the spedo may be bad or a wire has been broke between the speed sensor and the spedo

check all your wiring from the light to the fuse panal. that should fix it