Trouble Logging Speedo Input

[JFastsc92]

I've had my M-500 unit for quite some time now(4+years), and since I've owned it, I've never been able to get my VSS to display or log correctly. The vehicle is a 92 Ford Thunderbird SC. I have tapped into the Speed sensor at the EEC connection and inputed it into speed 1 on the logger harness. When the car is stationary, I get jumpy readings. If the car is moving, I get inputs on all extremes on any scale that I give it, always in a random manor.

Can you provide some indication of what my frequency range should be that I enter into the software. Just a ballpark would be great to get me in the general area. Do I have to install any type of noise filtering device? Should I tap into the signal at the car's gauge cluster? Should I tap into the signal at the sensor itself? Any help would be great.

Here is a link to the EEC pin-out. Pin 3 is where I tapped into the signal (Drk-Green/White Tracer).
http://econtent.autozone.com:24991/znetrgs/repair_guide_content/en_us/images//0900c152/80/06/bb/d4//large/0900c1528006bbd4.gif

Thanks for your time.

[PLXSupport_PL]

You'll have to do an experiment with it. Drive your vehicle and observe the frequency at 10,20... 50 mph. Based on the frequency, you'll have able to calculate the conversion factor.

For example if at 10 MPH your frequency is 30, you'll know that your relationship is 10/30

[JFastsc92]

My issue is that it jumps all over the place when the car isn't moving.... I'm wondering if the signal is noisy, or I need to tap into it elsewhere....

[JFastsc92]

How can I directly read frquency using the logger?

[PLXSupport_PL]

No that's planned to be a feature on the R-800

[JFastsc92]

As an update....

I tried logging the input from behind the car's cluster vs. at the ECU with the same result. It's getting signals at every end of the scale no matter what correction factor I enter into the logger. I've tried .001, .01, .1, 1, 10, 100 ect, just to see if there was a difference. It seems like it's not getting a clean signal.

I've tried it on both of the speed inputs on the unit itself and I get the same results. This should rule out any manfuntions in the M-500...I think...

The vechicles speedometer functions normally. The entire unit gets its power and ground from the ECU wiring harness.

Should I tap elsewhere for the reference grounds and power source?
Is there a chance that the unit is malfunctioning?
Can I install some sort of noise filter?

I've tried everything that I can think of with the same result.

[PLXSupport_PL]

Yeah it looks like you're getting a bunch of noise. Do you have an oscilloscope where you can check to see if you're getting a nice clean signal?

Check your ground. That may also be the problem.

[JFastsc92]

I don't have access to a scope, but the factory speedo works without any issues.

The unit is grounded at the ECU wiring harness. The same ground that the ECU uses. I figured this would provide the best place for the same reference. Should I just use a chassis ground instead? Will that affect my logging accuracy from my other signals?

[PLXSupport_PL]

It shouldn't.

[JFastsc92]

Another update.....

I re-did all my taps into the factory computer. I used a terminal block behind the glove-box to make my connections to the logging harness, and re-wired and soldered all the connections at the computer and heat-shrunk all the wires. I also relocated the ground to a chassis ground rather than tap it from the vechicle's harness. The main 12volt power is still being tapped at the vechile's ECU wiring harness. I also installed a 5am fuse in series at the 12V connection which is then split into the M-500 and the G-sensor.

All other signals logg flawlessly. The speedo signal is still irratic, and gets pulses even when the car is stationary AND when the units in the logger speed calibration are zero.

I did not have a chance to try the input on speed2, but I'm 100% certain that all the taps are solid and secure, the ground has been relocated and has a resistance of 0.4 ohms. I'm trying to work the problem and isolate anything that could cause this issue. I'm now leaning towards that the unit itself maybe malfunctioning from the beginning. Is there anyway that I can test the unit myself to ensure that it is working correctly? Could the 12v power source be causing signal noise? Again, that's for all the support so far.

[JFastsc92]

Any new suggestions?