(a) A manufacturer will be notified whenever the Administrator has determined that a substantial number of a class or category of vehicles or engines produced by that manufacturer, although properly maintained and used, do not conform to the regulations prescribed under section 202 of the Act in effect during (and applicable to) the model year of such vehicle. The notification will include a description of each class or category of vehicles or engines encompassed by the determination of nonconformity, will give the factual basis for the determination of nonconformity (except information previously provided the manufacturer by the Agency), and will designate a date, no sooner than 45 days from the date of receipt of such notification, by which the manufacturer shall have submitted a plan to remedy the nonconformity.

(b) Unless a hearing is requested pursuant to § 85.1807, the remedial plan shall be submitted to the Administrator within the time limit specified in the Administrator's notification, provided that the Administrator may grant the manufacturer an extension upon good cause shown.

(c) If a manufacturer requests a public hearing pursuant to § 85.1807, unless as a result of such hearing the Administrator withdraws his determination of nonconformity, the manufacturer shall submit the remedial plan within 30 days of the end of such hearing.