A Blast from the Past ! REDUX.
For 1989-1995 USA Sidekicks and Trackers only.
There are no over-the-counter OBD1 Suzuki tools sold, not at Autozone, PepBoys, Advanced Auto or Napa. Nothing. SAVE YOUR TIME AND ENERGY !
Nor do their mechanics have them, or the clerks.
The is but only one tool (below $400 and still working, unlike the many dead Tech1 tools sold on fleabay)
Fact 1: Suzuki never published the protocol. (Signaling levels, methods, timing rates, command sets or anything at all , save the 1 pin comm. line location, in the DLC)
Fact 2: There is no OBD1 standard between car makers, OBD1 is unique to just Suzuki in this case. (that is why USA invented OBD2 to solve that tiny problem, LOL !)
Fact 3: The only real tool made today is this (was list I looked)
All I know is here, not much, in the next link.
The hacking scan tools are all here.
Back in the day, the shops used this tool called a TECH_1.
Most shops today, do not have this tool, and if 25 years old (most are) , probably died, long long ago from long hard use. (rat nasty shape)
We see these sold on fleabay for insane prices ($400 on up), and also needs the RARE Suzuki plug-in's to work with this car. (good luck finding one that works!)
| The
TECH1 below. (1989 old) RARE to the max and the plug-in for Sidekicks
100x more rare. By the then Vetronix company (now BOSCH). That membrane switches are long ago dead/ weak/cracked and flaky. Warning, this tool has a bug in it , that reports ECT sensor temps wrong! (with some plug-in's) Getting revisions, for this tool , are Impossible. (Suzuki is Chapter 11 in USA) 
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FUEL TRIM:
Short Term Fuel Trim = STFT.
Long Term Fuel Trim = LTFT
The OXYGEN sensor , the O2, is used to calculate TRIM. if its bad or exhaust leaks are near it, all the below is useless.
As you drive the car the ECU stores the trim it used to get STOICH fuel ratios.
Normal engines run naturally a touch rich (untrimmed) for obvious reason, is that lean burns head poppet valves (runs too hot) and when running wide open throttle , trim is not used. and must be rich then,
So the trim will be, naturally reduced, to lean , at say light flat not to fast cruising...(closed loop cruise)
The ECU will remove fuel (in the equations) via the TRIM value to attain, STOICH fuel trim and max MPG.
Short term trim changes way to fast for any human see or to read or comprehend the data, So we watch only the LTFT.
Some ECU's store trim (past reading) in a table based on speed and loads. (old GM books (cira 1985) document this very well, but not Suzuki! )
This allows the ECU to guess in advance of your next actions. (say going 50, and want go 60mph, the ECU can preload injection rates, just as you reach 60 to get better Drive-ability)
LTFT - Long term fuel trim Gauge values 118 is NORMAL (so says, all Suzuki books) it goes a touch lean to correct the natural rich state. (the numbers are a binary , 8bit byte , 2 to the 8th power)
| 0-----------------------128
--------------------------255 LEAN____________Perfect_________________ RICH |
the ECU always adds the STFT to the LTFT to calculate injector pulse width ( calc. fuel demand).
I do not have full documentation on all parametes.
If you see the LTFT way way off, maybe there is and exhaust leak at the 02s sensor, The 02 will slam to 0volts and this old nasty ECU goes SUPER RICH, (cured mostly with OBD2 rules and laws, later in 1996)
less is more... all this is (water under the bridge stuff)! in 2015.
ver 8 1 -20-13 , revised 12/2015, to make it shorter. sweeter...