Fix one thing , break another - P1875

[fixkick]

Taking care of sick family members in and out of the hospital as well as sick pets I haven't had much time to look into this in greater detail.

I took the speedo cable reduction box off and have been driving the vehicle for a while with NO P1875 error codes being generated so it can be said to be confirmed that the reduction box, while correcting the speedo is in conflict with the VSS(2) on the Transmission.  The speedo reduction box is about 12% different to compensate for the tires, which is greater than the 10% difference the manual says the gauge cluster VSS and the transmission VSS can differ.

I wonder if I could count the pulses from the reed switch at the speedo and reduce them by 13% with a micro controller such as an arduino to again 'match up' the VSS1 and VSS2 sensors. 

Is it just one wire for the reed switch to the PCM ??  Trying to find this out (and color) in my FSM wiring diagram.

There are many examples of reading and generating pulses on the arduino but more research is in order. 

https://www.fixkick.com/sensors/tests/vss-testing.html  #6 tells me.

As you spin that port, the VSS opens and closes many times,  0ohms, infinity, zero ohms, infinity , over and over.  that is a good switch if in beep mode it beeps over and over.

If I could put an Arduino or other controller inline between the speedo and the PCM and count the pulses from the reed switch and generate the same amount minus 13% and send it back into the PCM I think it might work.  

Where am I going wrong?

98 sport with 2.3L engine. stock ECU  stock TCM"


you are not going wrong
the Suzuki has 2 VSS, sensors, and they do not agree now. 
yes it is a reed switch in the speedo,, I have photos of all this, in the main page.  The reed switch no voltage refr. it  is only a switch. (makes it super simple to emulate)

the main cable, runs VSS2, in the head.
the rear of the tranny does VSS1. to the TCM, box.
both must be changed and the same way (RPM ) or it will set  DTC error, (conflicted, or as jeeps do, Incongruity.)

the speedo cable turns the speedo head, and that makes ODOM work and MPH and the VSS2 clicker work..


REDUCTION,  why that?    Big tires are speeding ticket getters. and reads slow.  
big tires have larger circumstance,  this makes the rear (drive) prop-shaft run slower not faster, and the MPH reads slow,and ODOM read less.
the axle I guess is 5.125:1 ratio, this is gear fixed, so as the end axles show down so does the front pinion gear and drive shaft
the speedo cable measure the rear drive shaft RPM (in any gear)
So any cable speed change box is speed up box. gear up, a  the cable cures 1 problem.  (unless thinking the cable turns the rear  wheel) relativity wrong.

the problem is there are 2 sensors. (my jeep has none it uses ABS sensors to do speed, all 4 and averaged, says jeep) so this shows the great variance on how this is done.
most cars have just 1,  the rear of tranny electric hall speed sensor.  (doing 2 things, shift points 4speed, and MPH ,etc) 
Not suzuki this is what makes the Suzuki so different.

yes and Arduino or any tiny micro can do this.  speed up.  10%   (at any given true speed, the tall tires, make the drive shaft run slower, 10% more circumference.
I do not have any 1998, ECU nor TCM schematics, so can not comment on wire colors.  to TCM.



the sport is not wired like any G16, nor do they share harnesses nor PCM really the Sport is and early GV< grand vitara, (beta version, LOL)

the PCM changed every year,  96, to 98 they changed alot, and the TCM did not change the 3 years, 1 P/N exists only.
your 2.3L i guess runs off a 1998 PCM/TCM right so only 98 PCM drawings match.

the sport did not move the TCM into the ECU in 1997 like G16 did. (and rename it PCM) this did not happen on the sport. (yes complex )

no.  and has a very odd setup the sport 1997,  where the ECU monitors the shifter and VSS2 and TCM monitors VSS1. VSS1 is a way more stable and accurate sensor to TCM)
and TCM is still in the dash all by itself, and they work as team in (96-98)
that means the TCM has its own, VSS, and the ECU has the other, in 1997
I have no drawings of the 1998. TCM nor PCM.
all sellers of TCM 38880-77e21 , sell it for 96 to 98 sport, so the words above about 97 are true. the master Suzuki shows 1 TCM for 3 years, and only one 1998 ECU  for USA.

each year has its own ECU. (and country)

and it does for sure have VSS1 inputs, to shift the box it does,  and IS WAY more accurate than that funky jumpy VSS2 in the speedo head.

the ECU VSS is yellow wire, and blue (or yell-red) 


VSS1 is seen her on the 4SP AT. ID #26

p/n 24791-57B00  id 26  this sensor goes to the TCM. for accurate shifting and accurate MPH speeds sent to the ECU.
if car is 4wd,  IS YOUR CAR 4WD?

the 4speed AT, has rear vss sensor, and the TCM sees 2 more switch sensors on top of the transfer case, these are 4wd yes/no binary logic and High.Low range logic,
so when in 4wd High the speed is 1:1 if in low the TCM sees the low range switch in low and does the math. ( a reduction of VSS speed at the LOW gear ratio)


not sure what you car has I will have to go back and read all ports, on this custom car.
sorry and next.