that is true.
but some cars running obd1 , can be scanned,. (i have one)
like all GM cars and even older, , some ford, , Honda's . Toyota;s
but this car is GEO, (underdog, but is really what. a Isusu.)
Isuzu's cars are mostly not raced or sold here now. so who's going to make scanner for such a rare car and engine and EFI?
there is no OBD1 standard, each company uses a unique design.
OBD2, in 1996 a USA invention is a standard and all tools work.
what you have is the old blink codes. wink wink...
all OBD1 cars work like this (or very close)
you connect a jumper wire, and the CEL lamp flashes codes.
so is the CEL stuck on? running.
must come on key on, bad lamp or bad ECU.
you can check out Isuzu Impulse
Example storm post..OBD1991 (USA)
To put the ECM (Engine Control Module/Ignition Control Module/Engine Computer) into diagnostic mode, where it will flash codes at you using the "MIL" (Malfunction Indicator Light or "Check Engine" light), short pins 1 and 3 of the ALDL/OBD1 connector using a paperclip. When you then turn the key into the on position, the MIL should flash once, then pause a bit, then flash twice. That means code "12." If there are other codes, they will be flashed out as well. All codes are two digits.
end quote, on storm
but where is the connector DLC?
and which pin is 1 an 3
so. we google more, or look it up in alldata.com like most do.
that was the 1st google hit, using clear text human questions.
DLC jumper storm or Impulse.
or diagnostic jumper Impulse.
join a Geo storm or inpulse forum and ask for scan tools.
they will be custom tools. (or hacked, as i have done)