flywheel speed sensor
 

Has anybody developed a test method for the flywheel speed sensor.

Measuring resistance will tell you if it’s dead or alive, but what about if it is marginal? i.e. working but putting out erroneous pulses, or missing a revolution occasionally.

It might be the source of a misfire and I would like to know before I waste time replacing it.

You can use a scope and look at the wave... But I have a special tool for that that I got from snap-on years ago. I bet if you had a DVOM that could show a graph you could still do it though.

IIRC, Bentley says to test the reference sensor with an oscilloscope and test to ### "sine". WTF???

Yeah, I'll just run out to the garage and hook up my "oscilloscope". Hopefully the "sine" will be up to specs.

There must be an easier way.

I am going to answer my own question ;)

I used a digital multimeter with a frequency counter (marked Hz)

I disconnected the sensor cable at the LH inlet manifold and made up test wires to connect the pins 1 to 1. Then I spliced in 2 x 8' wires between the 2 lower pins and ran these inside the car.

To confirm, you should get about 1.2k ohms between these wires.

OK switch to Hz mode and watch the meter.

The signal should rise and fall with engine speed.

I got approx 6 KHz at 3000 rpm, which equates to 120 pulses/rev.

More importantly the signal did not jump all over the place when the engine was misfiring. Based on this I am assuming the sensor is OK....