tux Posted February 20 Report Share Posted February 20 (edited) Some time ago I was trying to grab the VSS Signal from the read switch to input into my ECU. Someone else was also trying to do the same. I think that post was lost during the great outage. Anyways... after many electronics projects and owning a volt meter (and properly know how to read circuit diagrams) I finally figured it out. The VSS Signal comes from a reed switch. That reed switch only switches a ground signal. You can grab the signal from one of the connectors, but I wanted to do non-destructive. I grabbed a ring terminal and attached it under the screw directly to the right of the speedometer. You want to use the lower of the two screws. I'm going to call it VSS-Out This is a floating ground. So to use the signal, you need to add a pull up to 12v (for most applications, 5v for others). This gives you a high signal (+12v or +5v) as the normal state and a low signal (ground) when the switch activates. There are 4 pulses per revolution, resulting in a square wave (⎍⎍⎍) . This should work for just about any ECU unless the ecu is expecting an AC Sine wave or VR Signal. You will need to attach a diode inline from VSS-Out if you are expecting the intermittent wipers to still work, abs, or the cruise control. The line on the diode should point towards the cluster. Attach a wire to the opposite side of the diode with a 10k resistor and connect the other leg of the resistor to 12v. Then from the side of the resistor opposite 12v you can attach the wire to the ECU. I attached a basic diagram Edited February 20 by tux wrong image 3 Link to comment Share on other sites More sharing options...
psu_Crash Posted February 22 Report Share Posted February 22 (edited) What are you doing with the signal? Edited February 22 by psu_Crash Link to comment Share on other sites More sharing options...
tux Posted February 22 Author Report Share Posted February 22 Input into my aem for hi idle, 2 step and boost targets based on which gear I’m in. it determines the gear I’m in based on rpm and vehicle speed. Link to comment Share on other sites More sharing options...
psu_Crash Posted February 24 Report Share Posted February 24 Nice. I have considered doing something similar using a GPS module for speed and the ABS pulse for wheel speed. Then tie that back to my ECU for traction control. The VSS signal is likely to be more accurate (as long as you aren't spinning). I use a Garmin GLO 2 GPS module for datalogging already and it is pretty darn good at 10Hz refresh rate. Link to comment Share on other sites More sharing options...
tux Posted February 24 Author Report Share Posted February 24 For sure. I don’t want to pay for a gps module just for vehicle speed. I’d rather 20cents in components and grab the signal from the cluster. i may try to retrofit a mk60 abs module into the car at some point, but that would be a forever project for me.. probably Link to comment Share on other sites More sharing options...
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