Trouble shooting question Eng Speed Sensor

[twisted60]

Good day,
Couple questions:
First question :
I’m trying to understand the Engine Speed Sensor, looking at the trouble shooting guide in ™ …387-24-1 section 2 pg 402 it says .3 volts min at idle but it doesn’t say a/c or d/c. I see it marked as a/c in the 4L80 supplement,,, so should I read A/C or D/C on my multi meter when doing test from section 2 pg 402 ?
Second question :
The TISS and TOSS sensors, should they read resistance while engine is running ? Why I ask is I'm doing my best to understand the transmission system, I read resistance on the TOSS sensor while engine is running and not running but I only read resistance on the TISS while engine is not running. Is that correct ?
Thanks

 

[Mogman]

Resistance when not running, all transmission speed sensors put out AC when in operation.
The exception to this is the RPM sensor on the back of the early engines for daig use, they are simply a reed switch, open or closed

 

[owensexport]

Good day,
I’m trying to understand the Engine Speed Sensor, looking at the trouble shooting guide in ™ …387-24-1 section 2 pg 402 it says .3 volts min at idle but it doesn’t say a/c or d/c. I see it marked as a/c in the 4L80 supplement,,, so should I read A/C

It should be a fairly rough AC signal. All it does is inform the Transmission computer
that the engine is running and to turn off the TRANS led (Unless there is a fault of
some sort)

 

[Guyfang]

We have the same kind of speed sensors on gen sets. RPM = HERTZ. As long as the engine speed stays consent, the AC voltage stays consent. Not rough at all. It is an inductive AC. By moving the speed sensor in or out, you can change the AC output.

 

[Mogman]

The TCM uses the crank sensor for engine rpm, nice sign wave, 4X the crank speed on the 6.5L.