Cruise control: Diagnostics

WARNING: This page is about a different car, the 2001 Saab 9-3. However, it is still accessible from the selected car via links, so may be relevant.

The diagnostic tool contains a menu that indicates the condition that has not been fulfilled if cruise control cannot be engaged. Another menu indicates the reason why cruise control was disengaged when it was last used.
If the input from the brake light switch is continuously B+, diagnostic trouble code P1576 will be generated.

If the input from the brake light switch is continuously 0V, diagnostic trouble code P1577 will be generated.