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The ABS control module , will be supplied power, from both ignition and battery power sources. Through fuses. Less than full battery power or alternator power could set the code OR a bad system ground. Find the related fuses, and check for corrosion, and good power through the fuses, test the control module wiring harness, ground wire, for zero ohms resistance to ground.
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.