Tighten Gas Cap
WARNING: This page is about a different car, the 2007 GMC Sierra and 2007 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The instrument panel cluster (IPC) illuminates the TIGHTEN GAS CAP message in the driver information center (DIC) when the engine control module (ECM) detects a low fuel pressure condition. The IPC receives a class 2 message from the ECM requesting illumination.