Sorry I got the year wrong. When replying, I wasn't looking closely at your post title, but rather at the post model/year fields where you indicated ALL years and somehow remembering a 1990 240 thread I had just been reading.

As I noted, that means your 240 should have ABS OBD, although it's possible your 1992 was like the 1991s without ABS OBD. You can tell by looking at the diagnostic connector under the hood. Look down into port 3 of the A connector block. If it's vacant (you can see right through) then no ABS OBD, otherwise there will be a female connector in there to use to access the ABS controller. The standard procedure is in the 700/900 FAQ here
https://www.brickboard.com/FAQ/700-900/BrakesABS.htm#ABSDiagnosticCodeRetrieval

If the ABS warning indicator is lit then there will be up to three trouble codes stored. The code(s) will point you to the problem sensor(s) or things like the brake pedal switch or the control module itself. Note that if the code points to the brake pedal switch, the signal may come off the bulb out sensor relay connector rather than directly from the brake switch, in case you've done any wire butchering there to bypass the bulb out relay.

Please post back with your progress and eventual diagnosis.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now