My Suzuki  Factory ECU OBD1 scan tool usage and communications protocol :
circa 1995 (end of OBD1)   See home made tools here. Hacked.


ECU  Factory Tech 1 full scan tool output  (Suzuki OBD1)

1995 PUB. list:   (  I merged the 8v and 16v values in to one table ,  all lists 89-95 combined.  OBD1)
 
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 driveablity or MPG issues.

FUNCTION
UNITS
TYP.VALUE   and RANGE
ENGINE SPEED RPM 800 50  0-9999
DESIRED IDLE  R RPM
ECM cont. varies   0-2000
ENG. COOL TEMP C/F
176-194F typ.   -40 to250F
8V Intake Air Temp
C/F 149-167F typ   same
16V MAS AIR FLOW  MAF.
g/S
3.1g/S 
THROTTLE POSITION volts
.85 to .95Volts [idle] (0 to 5.1vdc  WOT)
TROTTLE ANGLE 0 at idle   up to 90 max.  (wot=  80 typ)
8V  MAP Manifold Air Pressure
kPa,V 39 kPa / 1.56v   0-125kPa range, 0-950 mmHG
8V BARO
kPa,V
98 kPa / 4.00v    same range above, use only for altiude
HO2S (OXY)
mV
10-900 mV typ varies.        0-2500mV
O2 ACTIVATION true/false
active or not.  "Closed loop op's"
S.T FUEL TRIM na
127 typ counts     0 to 255  ( 128 is center pt)
L.T FUEL TRIM
na
118 typ counts     0 to 255  (128 is center pt)
SPARK ADVANCE 5-15   up to 60
INJ. PULSE WIDTH
mSEC
1.1-1.6 mSEC   0 to 65mS
IAC/ ISC AIR FLOW L/MIN
24-40 L/MIN   ,( 0 t0 250 max.)
IAC/ ISC  ADJUST MONITOR
%
0% typ and up   to 100%
IDLE SWITCH (TPS)
on/off
 on
8v THROTTLE OPEN SOLENOID
on/off
off
FUEL PUMP
on/off
on
EGR GAS TEMP (CALIF)
C/F 140 TO 145F   (32 to 470F ,max)
EGR SOLENOID
on/off
off
A/C SWITCH
on/off
off
POWER STEERING SWITCH
on/off
off
PARK/NEUTRAL POS
P-n or R-DL
P-n =Auto, R-DL manual
MPH/KM/HR
MPH/km/hr
0/0   -parked  (0 to 125mph max)
FUEL EVAP PURGE
%
0%  (100% max)  8v shows on or off.
RICH LEAN STATUS
rich/lean
switches  will show lean if  HO2S is low all the time. (or opposite)
SYSTEM VOLTAGE
volts
14-14.5 volts (20v max)  0 to 18.75vdc range
16 VCHARGING EFFi
%
10%   (100% max)
8V time from start
sec
0-510 sec and rolls

Notes:
Fuel trim is the amount of fuel the ECU adds or subtracts, to achieve STOICH  14.7:1 Air to fuel ratio (by weight);
The short term is like a lawn sprinkler , where is the water going? , Answer:  all over the place.  (fast corrections are happening)
As you drive the STFT slowly (seconds) transfers to the LTFT which zero's the STFT,  so that temporary changes are stored in the short term.  And long term changes in LTFT.
The Long term is like the water meter showing flow   (the equation , algebraic math is,  STFT + LTFT = Total fuel trim.)
Best practice, is to ignore STFT ,unless it sticks .  ( it moves way faster than you can see it, and for sure faster then any scan tool, can see it (refresh rates))  

The above LTFT of 118 shows ECU is removing  about  -10 % fuel  ( OBD2 uses percent) Very Normal !




The remainder of the above is chicken soup, to any modern OBD2 user.


This example data chart represents, what is displayed by the GM Tech1 scan tool.


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



8-3-2008
v2



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