Power Train – Power Distribution Module Module 286 (PT-PDM) Power Train (PT-PDM) The PT-PDM holds all of the power train related fuses and relays. • All engine fuses/relays • All transmission fuses/relays • All after treatment fuses/relays except DCU main battery feed (located in PNDB) • Sleeper power The power which supplies the PT-PDM is sourced from the Power Net Distribution Box (PNDB). This power is protected by a 175A fuse. It is important to note that the PNDB holds the bi-stable relay, which disconnects the battery when the relay is turned off power at the PNDB output. PT-PDM power is not maintained by the alternator if the disconnect switch is "thrown".
therefore the engine ignition relay, in the PT-PDM will fall out and the engine will turn off. The source of the ignition signal, on a WST, is Fuse F33_LD which is in the optional fuse block in the dash of the Western Star. The sole purpose of this line is to turn on the PT-PDM relay which then powers ignition for all the engine related ignition circuits. Page 1A-6 Rev (2.3) - Feb 2015