You're correct, we're just speculating about the SRS diagnostic light.

The right answer is still 1991 only. Sorry to be so stubborn, but the part number is the last word in "interchange" and those for the cluster circuit board are different 90 and 91. I can maybe guess the difference is in cruise, and that might not matter for a car without it, but can't be sure. Maybe your stare and compare of the physical units will reveal the difference.

Some other interesting year to year differences revealed by the parts fiche are the speedometer gauge changes. 88 is not the same as 89, but 89 through 91 are the same regardless of ABS. 92 and 93 are the same.

Another thing I learned from looking at the fiche: The Canadian market 240's only got one speedometer for sedans and wagons.

Not having ever owned an 88, I can't guess how the speedometer might have changed electrically prior to LH2.4 -- maybe the wire pin for the taximeter output? I suspect the part number change just reflected (ouch) the new matte finish.
--
Art Benstein near Baltimore

Dad: Someone who hopes his sons will turn out to be just like him, and who is afraid his daughters will meet someone who did.