joker2cv

Hello,
My car runs fine, but i was anyway checking the RPM and REF sensors as in this video


The resistance of both sensor is about 1,2kohm at the DME plug, the REF sensor voltage is ok but the voltage of RPM sensor is too high: i read about 4,5 ac volts. Is it too high or not? Probably a bad sensor or bad gap?

Tom M'Guinn

Resistance of 1.2k sounds good. The a/c voltage will vary based on engine speed, as the sensor generates the signal from the metal peg passing under it, so I'd say all is ok. Why did you test them -- is something wrong with the car? See more details at clarks...

http://www.clarks-garage.com/shop-manual/ign-02.htm

reno808

very good video

joker2cv

I read ckarks. The car is fine, but is strange a so high RPM sensor voltage output at starter speed.
I'm afraid that it could destroy something inside DME...

Tom M'Guinn

Without an o-scope, it's hard to measure the actual pulse amplitude, but regardless I would not be concerned at all if the motor is running fine. The amplitude is a function of engine speed and sensor gap, so it sees higher voltage all the time when you rev. There is a dedicated chip in the DME that protects the processor from the raw voltage -- it's sole job is to accept the raw sensor signals and output nice clean 5v digital pulses the processor can handle.