I personally had mine replaced. But Gazzer's post hinted that they actually repaired the board (solder reflow and a hardwire jumper or two) and put it back in. I've fixed many PC boards with broken solder and would have attempted this, too, had my car not already been in the shop for other routine maintenance. It was just easier to write the check.

PC boards are normally pre-fluxed (for lack of a better term) so the solder flows to the right places, and doesn't stick to the wrong ones. Obviously, you'd need to have the electronics-grade solder composition. (PC boards are usually soldered by immersing the entire board in a solder bath.) Again, I haven't done this particular repair, but Gazzer - a Volvo tech who can shine a little light on this - apparently has.

Looks like my ABS unit comes apart without a hacksaw.

I'm pretty good at repairs - including tough ones. I've done many things they said I couldn't do (e.g., rebuilt a turbo for $96 in parts). If my ABS/TRACS board goes again, I'll fix it myself regardless of gels, epoxies or other supposed obstacles.
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(98 S70 T5SE misc mods - mostly lighting - and red calipers) (92 940GLE)