By Michael McQueary

I remember my first experience with a scope, it was an old analog Tektronix that I picked up used at a scope shop a long long time ago. The first thing it helped me on was a Mopar dual pickup distributor. It would start, and then die. I hooked a channel to each of the pickups, and cranked it over to see what it would show me. I was surprised that nothing appeared at all! After getting the trace to show up on the screen by setting the proper scales, I was finally looking at my first real waveform on a scope. It showed me the start pickup was sending a signal, but the run pickup was dead. I replaced the assembly and the problem was corrected.

I was quite pleased with myself at this point, and I was thinking of what else I could use this marvel of electronics on for diagnostics. As it turned out, the old analog unit wasn't good for much, because of its straight-line ability, I used it less than my old Allen analyzer and even it had some labscope features.

In my all my years as a Tech, I have seen many changes along the way, and I have tried to keep up with them. At times it seems like things change faster than you can learn them, but I think that most of us manage to keep up. It amazes me when I think back to the sixties and how simple things were then compared to what we are faced with today. 

I have two of them, and I use them every day. They have the power of the big machines, but take a fraction of the time to hookup and look at something. Both of mine have a meter in them for looking at the simple things we do most often like voltages, amperage, ohms and so on. If you need to look at the signals with more scrutiny, that’s where the scope shows its ability. It allows you to see the signal over time and check its structure and stability. It allows you to see the signal at any speed you want, so you can look for intermittent loss of the signal, transients, or plot it over a long period of time. I am always finding new ways of using them that help me.

Don't get a false sense of security with these, I have learned in my 46 years of experience that all the diagnostic wonders in the world sometimes don't help beyond your gut feeling, and when your not getting help, that's all you can depend on, and more often it's right. Most often you might go looking for a glitch in a tps signal, and sweep it many many times and never see what your looking for, but it still creates the hesitation just off idle you feel, so you replace it on a gut feeling and its corrected. I certainly have had them show the transients in some of them, the wave forms are in the testing areas.

Over the years I have owned many different scopes, some with as many as 16 channels. Once I recall looking at 7 different wave forms at once if I remember right they were crank, cam, primary, secondary, injector firing, coil and injector ramps. I wasn't after anything, just wanted to see it. That being said. it makes a point, this is one of the things that makes them shine, is using them for looking at correlation of events in the wave forms of devices that need correct timing to do whats expected of them. An example of this is the importance of the correlation between the crank and cam sensor in order for the pcm to control ignition and injector events.