rpm output when engine off.

[mr_g]

I have found out, when the engine is off, rpm outputs the signal like 10 time lower frequency, cca 100rpm... My response was: WTF!

Does anybody know anything about this?

[lost]

TRY to use coax cable or sometihing shielded. got the same problem of ghost rpm with standard 1mm 2 wires when turnig key to acc on after few seconds.

[mr_g]

You think that VEMS doesn't send this signal? 

[gunni]

If you have cut the 12v to the ecu then it´s not possible.

[mr_g]

ECU has 12V, because I'm starting it up. But I have just added ignition signal,with no cranking, and engine isn't started. But VEMS is supplying 100rpm (cca 1.5Hz) signal on the rpm output. After cranking and starting engine, I would get about 10 times higher frequency, about 1000rpm (cca 15Hz)..

[gunni]

I have not had that happen.
Might want to up the pull-up resistance

What is it now?

[lost]

you get some interferance. from hi current wires to lambda or injectors. try removing all fuses except vems supply fuse and then check rpm for ghosts

Solved same problem with some hi quality coax. from vems to rpm trigger. I was getting for a few seconds like 300 400 rpm  but onley with the lambda fuse connected. and engine was off!

[mr_g]

So it's wbo2 heater creating interference?

[lost]

So it's wbo2 heater creating interference?

yes.

[mr_g]

Maybe the lower pull up resistor would do the trick...