I remember reading the post a few weeks ago, someone opening the ABS module with a dremmel and looking inside at the small circuit board with a magnifying glass He found a couple of areas with broken solder. He resoldered those areas, and sealed the box with silicone and his problem was solved. This reminds me of the common failures of the fuel pump and overdrive relays secondary to poor soldering, in the 240/740.

Since you have an extra one, take a chance and open carefully with a dremmel. Buy a good magnifying lamp and check the circuit board solder and resolder or clean those solder points. You have nothing to loose, and about $800 to save.

Please post back on the success or failure of your project.
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'88 240, '92 740, '98 v70 GLT John in Tampa Bay