What is the initial step to take if a PA4 train fails to take power?

Using the Motorman's Bypass is the initial step when a PA4 train fails to take power because this function allows the operator to override any malfunction in the control system that may be preventing the locomotive from receiving power. The Motorman’s Bypass is a critical tool designed specifically for situations where standard power systems are not functioning as intended. When engaged, it can directly enable the train's systems or allow the engineer to troubleshoot the situation without the immediate need for other checks that could delay resolution.

In contrast, activating the emergency brakes, checking fuel levels, or inspecting the track for obstructions are all responses that may come into play if a more significant safety or operational issue arises, but these are not the first actions to take in the specific context of the train failing to engage power. They can be subsequent steps if there are still issues after trying to bypass the control system.