Hi Pete,

Every primary coil circuit has an "end-stage" somewhere.

You could argue that the first end-stage were the Points. This was the final stage in the primary switching circuit.

Then the end-stage became an electronic switch and was fitted inside the Ignition module otherwise known as the Ignition amplifier(the little black box as fitted on the outside of the dist body of Ford Escorts in the 80's)

VM's then started fitting the end-stage inside the ECU, an example of this type of vehicle would be the Ford Focus with wasted spark.

Nowadays a lot of COP's have the End-stage built in to them.

So to sum it up the "End stage" is the electronic component that handles the current to switch the primary side of the coil.

Where it is fitted controls and sets your diagnostic route and testing plan.

If your end-stage is inside the coil, you can not scope the primary but you can look at the enable signal from the ECU.

Volt drop the feeds and earths, scope the enable signal and carry out a resistance check via an amp clamp.

Regards Mark