VSS signal-shows 0 mph or 158 mph all the time

[marksawatsky]

I have a standalone LHU in a RWD configuration so I am using a Dakota Digital adapter for a VSS signal, see it here: http://www.dakotadigital.com/index.c...rod/prd916.htm
The problem is that I can't get the ECM to recognize the signal so it will either show 158 mph all the time (when tuned to manual trans) or 0 mph all the time (when tuned to automatic trans). I have tried all the different kinds of automatic transmission adjustments but nary a blip. I know the VSS is sending a signal and I have sent the signal to several different pins on the ECM. I have sent it to C2, Pin 5 (Output Speed (Digital) 5V Sensor Reference), C2, Pin 8 (Output Speed (Digital) Signal) and C2, Pin 21 (Output Speed (Digital) 5V Sensor Return) while trying all the different automatic trans settings and manual trans settings. Is there some combo or setting I am missing? Any suggestions?

[Speedytec]

what type of VSS signal does the LHU normally get? 1 wire pulse signal (from ABS) or a 2 wire sine signal directly from a vr sensor (on gearbox f.i.)?

For my car (standalone lsj ecu) I had to modify a pulse signal with a capacitor to simulate the negative part of a sine; and it does the trick for vss input. ;-)

[marksawatsky]

what type of VSS signal does the LHU normally get? 1 wire pulse signal (from ABS) or a 2 wire sine signal directly from a vr sensor (on gearbox f.i.)?

For my car (standalone lsj ecu) I had to modify a pulse signal with a capacitor to simulate the negative part of a sine; and it does the trick for vss input. ;-)

I don't know but how did you use a capacitor to modify signal?

[Speedytec]

The P12 LSJ ecu uses a direct VSS signal from a 2-wire VR-type sensor. This gives of a pos/neg sine wave and the LSJ ecu probably triggers when this signal passes 0v.
In my car (Rear engined Opel Speedster) I have a 5v pulse signal coming from my ABS module. This 5v pulse has no negative voltage component, so my LSJ ecu does not "see" a propper VSS signal input with that.
But when you pass a 5v square wave through a capacitor; it blocks the DC component and when the pulse signal goes from 5v to 0v, the output signal dives below zero volt with a negative component. Just enough to trigger my LSJ ecu and I now get a VSS readout. A $0.01 solution. :-)

But the LSJ ecu is pretty old and most likely the LHU ecm (is that an E39A?) uses something more modern for the VSS signal input. Does it even have a VSS signal input pin?

(PS; I need to talk to you about your stand-alone application, as I have an DI 2.0 engine in my garage, an E39 ECM and a proper rear engined car for it... ;-) )

[marksawatsky]

My ECM is an E39A and it has a total of 4 pins that refer to some sort of VSS. I am willing to try a capacitor on the signal (hey, it might work, right?) but my local electrical supply house is run by a guy who scoffs and luddites like myself. Whenever I ask a question, he sighs then talks in a language I do not understand. What kind of capacitor do I need?

[marksawatsky]

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