The Pulses could be viewed as a percentage of time on vs time off - this could be interpreted by your meter as a "duty cyle" but the problem is the time scale - I'm not sure how your meter would deal with the pauses between sets of codes or matter the passage of time before and after the actual deliver of coded data. I have read these codes with an old analog meter but its kind of a pain in the neck.

Here is a link from fellow MB-shop member JIMF website that details how to make in impulse counter for less than $10 using Radio Shack parts (he even supplies the Radio Shack part numbers). Jim's site is an amazing collection of MB diagnostic info. The info is at the bottom of the following page.

http://pages.prodigy.net/jforgione/MB_X11.html