These instructions only apply to '90-91 model Reattas that have radios with TheftLock installed. The radios were used in the C/K trucks, including Suburbans/Tahoes/Yukons, from '95 onwards.

The procedure to unlock one is:

- Turn radio and ignition off.
- Depress and hold preset buttons 2 and 3
- Write down the first three digits that appear on the radio display
- Depress AM/FM, write down the second three digits that appear on the display
- Contact Delco Assistance to obtain a "Radio backup code"...

Then:
- Use the hours and minutes buttons on radio and install the 4-digit "Radio backup code"
- Depress the AM/FM button
- "SEC" should display.
- Repeat the last three steps to remove the original owner code.

Thanks to wws944, member of AACA Reatta forum, for this information.

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