Bruce, you were clear enough about using the meter and not the LED. I think I was answering too much from my own situation, where it would be tough for me to come up with two DVMs to use simultaneously, but I could probably lay my hands on hundreds of LEDs. Which in turn, leads me to explain why I speak confidently about this particular test point: I've traced the circuitry in the ECUs to a large extent with the LH2.0 and 2.2 and a lesser extent in the LH2.4s. So I recommend you connect an ordinary LED (no you don't even really need a 750 ohm or other current limiter - it is built in on the LH2.2 ECU) between battery positive and the test point. With something that goes on and off at about a one-second rate, I believe you will be able to visually gauge the duty cycle more effectively with the light than by trying to catch DVM displays.

Now, on the Fluke's duty-cycle function. I can't speak from experience here for one reason-- I have a Fluke without that function, but I know from using a scope and watching the LED the duty cycle often varies I guess as much as 30 percentage points between any two consecutive cycles. At such a slow rate with that much variation, any meter would have to average the reading over tens or hundreds of cycles, and I have no idea how or what kind of control you'd have over the Fluke statistically.

But, Bruce, my previous response never addressed the one part of your post that puzzled me. You said something about switching to voltage (from duty cycle) and seeing 14V on the test point. If my recollection of the LH2.2 test point is the same as mcduck's, there's no source for the 14V until you provide one externally. Unless--- you were measuring between battery positive and the test point. That would explain it. If you follow mcduck's suggestion to provide that resistor between battery and the test point, you could connect your meter between ground and the test point-- then you should at least see something flopping back and forth and a duty cycle if the Fluke can work at those low frequencies.

I know the car is gone now, but dig an LED out of some discarded piece of consumer electronics junk, or get one with new long leads from the Radio Shack (do you have those?) and wire some clip leads to it. You could put in a current limiting resistor-- it wouldn't hurt, and would make the thing useful for voltage tracing, but it isn't needed for the LH2.2 test point. Either way, definitely follow up with us on your emissions test results!

As for the "book", I thought the dwell meter technique was based on the frequency valve having a much higher switching rate, and one developed by synthesis in the K-jet lambda computer as a function of the oxygen sensor flips.

I've got an ancient tach/dwell tester that is simple as the seventies. It uses the meter's mechanical inertia to integrate the on/off time to scale deflection. It might do well on the k-jet, but you'd just see the needle bouncing up and down on the LH test point. So you can see why I was skeptical of some of those vague procedures given in the factory manuals and copied to Bentley and Haynes, and why I had pulled the ECUs apart to find the answers.
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Art Benstein near Baltimore