no on-off ratio

[mbshop]

we have this 88 300te. running rich. failed smog.
we can't read the on-off ratio. when we try to clear
codes we got no blink. nothing. we found a bad connector
but still nada. we replaced parts and still nothing.
so we can't clear the codes with the pushbutton unit(x11)
and with out this the computer won't let us read the on-off ratio.
i've seen this written up somewhere but can't find it.
thanks all,

george