An engine variable camshaft timing phaser (10) includes a sprocket (12) and a planetary gear set (14). The sprocket (12) receives rotational drive input from an engine crankshaft. The planetary gear set (14) includes two or more ring gears (34, 36), multiple planet gears (32), a sun gear (30), a first set of teeth (82), and a second set of teeth (40, 62). One of the ring gears (34, 36) can be connected to the sprocket (12) and one of the ring gears (34, 36) transmits rotational drive output to an engine camshaft. The sun gear (30) engages with the planet gears (32) and is driven by an electric motor (38). In order to bring the planetary gear set (14) to a locked condition, the first set of teeth (82) and the second set of teeth (40, 62) are mated with each other.