An electrical connector assembly includes, among other things, a connector that includes a connector lock arm that is cantilevered from one side of the connector to a free end. The connector lock arm has first and second apertures that are separated by a block. The assembly further includes a connector position assurance lock that has a base that supports a wave-shaped center lock arm that is received in the connector lock arm. The center lock arm extends to a nose that has a shoulder. The connector position assurance lock is slidable between unlocked and fully locked positions that respectively correspond to the shoulder arranged in the first and second apertures. The center lock arm has a bend joined to the nose by a portion that is parallel to the connector lock arm in the unlocked and fully locked positions. The center lock arm is configured to be deflected to an improper mating position with the portion arranged non-parallel to the connector lock arm.