DTC C0021-09: Brake Booster Performance - Component failures: Action
WARNING: This page does not describe the selected car, but rather 12 other vehicles, including the 2015 Jaguar XKR-S, 2015 Jaguar XKR, 2015 Jaguar XK, 2014 Jaguar XKR-S, and 2014 Jaguar XKR. However, it is still accessible from the selected car via links, so may be relevant.
- Check integrity of brake booster vacuum hose. Check and install a new brake booster as required