Signal divider for second speed sensor ECU input

[2JZR31]

This problem refers to an Aristo conversion into a R31 skyline.

I have been having a few probs with getting the speed signal to my ECU from the second (or is it the first speed sensor?). Anyway I don't even have the 3 wire sensor hooked up to anything ATM (sensor on the back of the A340L on the drivers side ). I know that the signal is processed by the speedo head and divided by 4 or 5 then comes back the ECU.

Apparently there is some simple circuit you can make with a PIC or something for a few bucks. Anyone know about this circuit, or some other approach I could take? I don't really want to buy 2x $320 speedo converters, just to get this and my speedo working.

[CrUZida]

The speed sensor on the passengers side of the box is the Primary sensor.
The one on the drivers side, which goes to the dash, and is then divided to 4 pulse/rev is for the BackUp sensor.

You'll only need Primary sensor for it to work properly. Backup sensor is only there for, err, backup.

[The Witzl]

Jaycar - Digital Speedo Corrector kit. About $45.

takes a pulse input, applies a correction ratio that you determine, and gives an output that's isolated from the input.

Sounds like what you need.

[2JZR31]

OK, so my probs probably reside in my other thead then. IE no ECT switches hooked up.

I would still love to see this circuit though as it will get my speedo working. Plus someone suggested that if the ECU does not see info from both sensors it may go into limp mode??

[2JZR31]

Jaycar - Digital Speedo Corrector kit. About $45.

takes a pulse input, applies a correction ratio that you determine, and gives an output that's isolated from the input.

Sounds like what you need.

The Jaycar unit only adjusts up to 100%, my probs are like 400% out. I actually built one and I cant get it to work at all

[CrUZida]

I've had both sensors not hooked up and there was no limp mode.
It wouldn't shift into Drive though, I had to leave the shifter in 2nd.

But it probably varies from ecu to ecu.

[Cool1]

The Jaycar unit only adjusts up to 100%, my probs are like 400% out. I actually built one and I cant get it to work at all

Get the circuit diagram into my hands and i'll look at modifing it for you

[2JZR31]

You guys are all legends. Thanks heaps for the input. Cool1, when I start trying to get my speedo working I will be in contact.

[SL666]

what signal did the r31 box give to the speedo?

[The Witzl]

Cool1 - i'll see what i can do for you tonight, i have all that at home

[2JZR31]

R31 uses square wave. The toyota sensor appears to work but is extreemly slow. I havn't tried it on the road, but the wheels have to spin bloody fast on the axle stands before it starts to register.

Here is what I found on my other working R31 with a multi meter. I could tell it was a square wave if I rolled the car very slowly by hand.

[SL666]

if the wheels have to be spinning fast, you need to multiply it..or the signal needs to be stronger... (i never had speedo issues, i have a speedo cable)

any idea how many pulses per revolution for the R31? and the 2j box?

[Cool1]

Cool1 - i'll see what i can do for you tonight, i have all that at home

Sweet. Just email it to me and i'll check it out next week.

[camrygt?]

Easy fix for dividing pulse by number is to use a 4017 chip. cost about a dollar or something from jaycar or dse. Basically a 1-10 counter chip. Give it a pulse and output 1 goes high another and output 2 goes high...all the way up to 10. By joining one of the outputs to the reset pin you can make it count/divide by 1,2,3,4... or what ever you want. then cascade two circuits to divide by any number up to 100.
I have used one in a cressida/1uz conversion were the speedo read something like 7 times too high and I couldn't get another signal to work.
search for 4017 and i'm sure there will be heaps of circuits or if you get stuck i'll dig one up for you.
very easy circuit to build and very cheap

[cambelt]

Im not 100% sure but i think VDO make a signal divider, it has 4 dip switches on it , Its a white and blue small unit with 4 wiring pins.