49 error code for the EV100 system indicates that it could be a possible scr 5 fault. I have had them in some cases when the snubber on the ev100 control system is the problem, however from what you have said while driving then activating the pump it seems to cause the problem, it may be that the more current draw is causing the scr to fail. So i would say possibly the thyristor is faulty. Before this though disconnect the logic plug and make sure that none of the pins are pushed back as a thyristor gate lead can also cause the same issue.
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