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...