At a glance
What can fail
On some Previa 4WD vehicles, the oil separator plate sits too close to the differential housing. During sustained highway driving, oil can leak from the air breather plug. Over time, oil loss can damage bearings and cause the front differential to seize, potentially resulting in loss of control.
What the fix does
A modified oil breather plug will be installed to prevent oil from leaking out.
Summarized — see the official notice for exact wording, dates, and contacts.