I sent the ABS control module out to Module Master in Idaho. They did a quick turnaround on the rebuild and guaranteed the work. However, as this did not fix my root cause I did some further investigation after removing the ABS control module and hydraulic pump assembly. It turns out there was a chafed wire which was consistent with the fault code. Instead of a $1,600 part and $600 labor (dealer repair prices quoted), it cost me about $0.10 worth of solder and probably a buck for shrink tube w/ sealant to waterproof the repaired wire splice.
This was on a 1998 ML320 with about 190k miles.
Ken

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2014 E250 Bluetec 4-Matic
2014 GL350 Bluetec 4-Matic
1996 Chevy Tahoe 4 x 4
2009 ML350 (sold)
2005 SLK350 (sold)
1999 E300 Turbodiesel (sold)
1998 ML320 (sold)
1991 300D 2.5 Turbodiesel (sold)