The tool that I have for reading codes on my 89Mighty Max is a miller
special tool. it has a volt meter built in and the codes sweep the analog
gauge. similar to manually checking codes on ford vehicles. the only
difference is the box plugs inline to the ecm at the right side kick panel.
The tool also is useful for checking sensor voltages.
Bryan

I generally refer to it as the Mighty Mouse.  This truck sat abandoned on
top of a hill for several years which is perhaps the reason it is still
usable.  It has 240K miles on it.  The engine was froze, the carb valves
were so froze I couln't move them with a hammer, the fuel pump was stuck,
and lots of stuff kinda rotted away from being in the elements with the hood
open.  The blower fan wouldn't turn because rats had built a nest in it.  It
had four flat tires.  The compression was rather low on the #3 cylinder but
it's improving with use.  The 4WD works fine and I've been using it as a
ranch vehicle to drag my roads and get firewood etc.  It's running so well
that if I could get the Maint Req'd light to go out and stop running too
rich I just might be able to get it to pass a California smog test but I
rather got the impression that they generally have trouble passing and there
are very few on the road possibly for that reason.  It was about as ugly and
neglected-looking as a truck can get but somehow it's looking better--I
guess it just needed to be needed.  So far the only money I spent on it was
for a new oil filter and oil.  Everything else I was able to finagle back
into functionality.  To me that indicates it's a very durable little truck
and probably worth fixing up.