Service manual

Power System 4-9
When AC is applied to the system, Vaux (auxiliary voltage) is asserted and is sensed
by the PCM. The PCM asserts DC_ENABLE_L starting the power supplies. If
there is a hard fault on power-up, the power supplies shut down immediately;
otherwise, the power system powers up and remains up until the system is shut off or
the PCM senses a fault. If a power fault is sensed, the power system attempts to
restore power and will do so if the fault is not sensed a second time. If the fault is
still present, the power system shuts down.
Since Vaux is independent of the power supply start, the AC plugs at the front of the
supplies must be removed to reset Vaux, allowing capacitors to drain voltage. All
power failures require this procedure since the PCM must sense a change in Vaux to
start the power supplies.