I am a firm believer that if you understand how a system works, it is a lot easier to diagnose. Basically, the distributor sends two signals to the ECU, a high resolution and a low resolution. One signal is used up to approx. 1800 rpm while the other is used above 1800. the ECU uses this signal to send a small voltage on the white wire to the base of an NPN transistor in the power transistor. the power tansister in turn pulses ground to the negative side of the coil. Now if i wanted to quickly test the coil and power transistor, i would turn the key to the on position and with a test lamp test for power at both the neg and pos sides of the coil. if ok, we have continuity. Now take the test light clip and hook it up to the positive battery terminal. Use the pointed end to tap the white wire at the power transistor. You should have a spark at the coil wire every time you tap and release the test lamp. If there is no spark, hook another test lamp to the neg side of the coil and do the tap test again. If the lamp pulses, the power transistor is good and the coil is bad. Still no pulse, we have a bad ECU. In answer to Franks question, a shorted power transister could take out the driver in the ECU as they are not thermally protected.
Conner