Hi JW,

Some good info on the 240 changeover years for ABS. Starting in 1989, the 240s and 700s got the newly mandated OBD (OBD-I) system in North America with the underhood diagnostic connector, a single connector then. Any models that got ABS had the early version of the controller that did not have OBD capabilities. Only select models and trim levels got ABS initially, such as the North America market '89 740 GLE (which I had). Volvo updated their ABS controllers to have OBD (OBD-I) capabilities starting in 1992 as the changeover year. If it was a calendar year mandate then that would explain a mid-1992 240 model year change you mention. I'm unsure of the 700 changeover years, but I suspect it's the same, carrying on until the last models were off the line in 1991. For the 900s, as a brand new series, they may have changed over earlier in 1991 with the introductory 940 SE (quasi 960 turbo) and GLE (16-valve) models, or they may have waited until the main 940/960 models started coming off the line for 1992. My reading elsewhere says the (later) '92 & '93 240 models did have ABS OBD on the diagnostic connector (port #3).

Contrary to what you seem to suggest, the underhood diagnostic connector with OBD-I fuel ECU, ignition, SRS, ABS, and power seat diagnostics continued in the subsequent 940 series right through until 1995, when OBD-II was mandated in North America starting with the 1996 model year. It was in 1996 that the underhood diagnostic connector was changed to the now required universal OBD-II socket in the console where an OBD-II reader was now needed to figure out what was going on and perform additional diagnostic tests and settings. ABS OBD continued on port #2 until 1995, then being integrated into the OBD-II diagnostic socket.

As noted elsewhere and in the FAQ, beyond basic issues at the sensors and their connector cables, the early surge protector (located next to the controller and not used in the later years) was a known problem area, especially the 10 amp fuse.

As I side note, on connector port #2 for the fuel side ECU, not only can you read out and reset diagnostic codes, there are also diagnostic tests you can perform, such as checking switches and sensors and operating devices, like rocking the IAC, operating the fan and pulsing the injectors (all described in the OBD FAQ section). What's not mentioned in the FAQ, and I'm almost certain I once saw it somewhere, is that you can perform similar diagnostic functions on port #3 for the ABS. One test I recall was pulsing the solenoids in the ABS module, which not only proved they could operate, but was useful for bleeding the brake lines through the ABS unit. I can't find that procedure in my manuals or a quick google search, so I may have been incorrect or it was for a different car. If someone can find a reference for that or any other ABS tests you can perform at the diagnostic connector, perhaps they could note it in a reply here.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now