Though it's a good idea to try to eliminate other possibilities, there's a good chance it's A) bad crimps that effect *some* operations, i.e., it will return specific codes, or B) a faulty ABS module.

PLEASE, PLEASE, PLEASE REPORT THE PROBLEM TO THE NHTSA, the people in charge of forcing recalls. Once you've had it determined that the controller is faulty, document it at *** http://www.nhtsa.dot.gov/cars/problems/ivoq/default.htm *** Without sufficient complaints, neither the NHTSA or Volvo will do anything about this very commmon issue.
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David \\ (98 S70 T5SE Black, misc mods (mostly lighting), red calipers) (92 940GLE)