I'm in the process of putting some finishing touches on my ECM bench. While I've managed to simulate the majority of the signals to the ECM with success, I'm having problems with the vehicle speed sensor signal. My .bin is set so that Option Word #3, bit 6 is clear (should indicate an optical VSS is present). I've put together a simple 555 timer to generate a 0-5V PWM to pins B9 and B10......

Has anyone had any luck using this option on their vehicle? If so, how did you connect B9 and B10? (It's entirely within the realm of possibility that I've managed to smoke the inputs due to improper hookup during my debugging sessions!) One of the things I question is whether or not the signal should be 0-5V or 0-12V. Another thing that worries me is a recent post about the 730 optical VSS where it appears there's quite a bit more processing relative to the 749......

Any help would be greatly appreciated!

 

Try C6 and set to optical.
I've only seen maybe one post on it in a few yrs.
But bench users are a small minority.

BW told me in an e-mail.

I can mail you the schematics if you don't have them or Ludis is stil MIA.

 

5v square wave signal.

In fact, the values my bench uses are a 250K pot, 1uF capacitor, and 10K and a 5.6K resistors with a 555 for VSS.

Swap out the 1uF cap for a .15uF cap for triggering the ignition module.

Set bin to optical, and tap signal to C6.

 

THANK YOU!!!!

I can't tell you how frustrated I was getting trying to get this to work by using the wrong inputs!! It's working perfectly now! Although I feel pretty dumb that it didn't occur to me different input pins would be needed for optical vs. mechanical, it's offset by the happiness of seeing a non-zero VSS being reported!

Thanks again!