To redeem a code on your iPhone:

  1. In the App Store, tap your iTunes account icon in the top right corner
  1. Tap on Redeem Gift Card or Code link
  1. Tap Enter Code on the new sheet that appears
  1. Enter in the promo code
  2. The App Store will ask you to enter your iTunes password (at least it should)
  3. On success message, open the Car Maintenance Reminder app. On your vehicle details page, next to the History section, tap the export button (it’s a box with an arrow pointing up). You should have access to download. If you still see the Unlock Downloads page, tap the Restore Purchase link and it should work.