whats wrong with my tacho output ?

[2swe]

https://www.youtube.com/watch?v=Jtz7cs_PC9Y

MS2 tacho out, using relay coil circuit (my mk1 golf gti rev counter needs it).
1k resistor between JS0 and DB37 output pin, the rest of circuit - relay coil and 2N5551 are behind cluster, far from MS case.
this is what my oscilloscope sees on MS 12v supply

I made this video in MS test mode, but believe me, if I turn the tacho output on while engine running, it starts to missfire and TunerStudio goes offline immediately..

[slow_hemi6]

Usually a capacitor is the go.Check out this thread http://www.msextra.com/forums/viewtopic ... 43#p373243

[2swe]

thanks for reply Luke.

I have added an EDIS capacior to relay coil positive, and I also rewired MS 12v supply, now I run extra wire from battery positive through small relay (key operated) and fuse to MS.

12v supply looks good, no spikes, but Tuner Studio keeps going offline as soon as I turn the tacho output or IAC1 pulsing ON..

[2swe]

replaced USB cable with RS232, now TS stays online..