Suzuki  Factory ECU OBD1 scan tool usage and super secret (Suzuki) proprietary communications protocol : 
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)



WHAT YOU WILL SEE IS THIS DATA:


1995 USA Published factory list:   (  I merged the 8v TBI and 16v MPI values, in to one table (see MAP and MAF together? )
 
Values are for a hot engine idling and not moving , 0 mph.

Items in blue are 8 valve and 16 Valve differences.

Items in Red are very critical items for troubleshooting drive-ability or MPG issues.
The OBD1 PARAMETER list.  (using OBD2 jargon, this kinda like a PID list)
The scanner can see what the ECU sees in near real time (live data). This data is extremely useful, to fast accurate repairs.
0
FUNCTION
UNITS
TYP.VALUE   and RANGE
1
ENGINE SPEED RPM Actual.
RPM 800 50  range is 0-9999
2
DESIRED IDLE  RPM (800 or 1000?)
RPM
ECM cont. varies  range is  0-2000  (800 is normal hot idle)
3
ENG. COOLANT TEMPERATURE C/F
176-194F typ.   -40 to 250F  , Mine is 190 A custom STAT.
4
 Intake Air Temperature (missing on 1992 MPI engines)
C/F 149-167F typ.  (will be at ambient temps at cold start) as is above.  
5
16V MASS AIR FLOW  MAF.
g/S
3.1g/S   or under load,  up  to 55 g/S  grams per second !
6
THROTTLE POSITION volts
.85 to .95Volts [idle] (0 to 5.1vdc  range)   4v is about WOT.
7
TROTTLE ANGLE 0 at idle   up to 90 max.  (wot=  80 typ)
8
8V  MAP Manifold Air Pressure
kPa,V 39 kPa / 1.56v   0-125kPa range, 0-950 mmHG
9
8V BARO
kPa,V
98 kPa / 4.00v    same range above, use only for altitude
10
HO2S (OXY)
mV
10-900 mV typ varies.        0-2500mV
11
O2 ACTIVATION true/false
active or not.  "O2 Closed loop status"
12
Short term FUEL TRIM  = STFT
see scale
127 typ counts     0 to 255  ( 128 is center pt)
13
Long term  FUEL TRIM =  LTFT
see scale
118 typ counts     0 to 255  (128 is center pt)
14
SPARK ADVANCE 5-15   up to 60  (mine tops out  at 45 light load, high RPM.
15
INJ. PULSE WIDTH
mSEC
1.1-1.6 mSEC   0 to 65mS  Super Useful !
16
IAC/ ISC AIR FLOW L/MIN
24-40 L/MIN   ,( 0 t0 250 max.)
17
IAC/ ISC  ADJUST MONITOR
%
0% typ and up   to 100%
18
IDLE SWITCH (TPS)
on/off
 on at idle
19
8v THROTTLE OPEN SOLENOID
on/off
off  (TB dash put VSV status)
20
FUEL PUMP
on/off
on cranking and running. May turn off, if spark is lost.
21
EGR GAS TEMP (CALIF)
C/F 140 TO 145F   (32 to 470F ,max) Thermoprobe device. EGR main.
22
EGR SOLENOID
on/off
off  (on cruising , off at idle or W.O.T)
23
A/C SWITCH
on/off
off  (fast idle request) 1000 RPM now.
24
POWER STEERING SWITCH
on/off
off  (P/S overload, fast idle request) 1000 RPM  now.
25
PARK/NEUTRAL switch position.
on/off
PRNDL status for A/T . changes ilde controls in DRIVE ! in gear.
26
MPH/KM/HR   VSS sensor input.
MPH/km/hr
0/0   -parked  (0 to 125mph max) (from speedo head,  reed clicker)
27
FUEL EVAP PURGE valve state
%
0%  (100% max)  8v shows on or off.
28
RICH LEAN STATUS
rich/lean
switches  will show lean if  HO2S is low all the time. (or opposite)
29
SYSTEM VOLTAGE
volts
14-14.5 volts (20v max)  0 to 18.75vdc range
30
16 V CHARGING Efficiency
%
10%   (100% max)
31
8V time from start engine up.
sec
0-510 sec and rolls

refr: 6E3-A-14  and 6E2-A-10  FSM  1995 pub.




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...