Check Gas Cap Message
WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The powertrain control module (PCM) sends a class 2 message to the driver information center (DIC) illuminating the Check Gas Cap message when any of the following occur:
- A malfunction in the evaporative emission (EVAP) system and a large leak test fails
- A malfunction in the EVAP system and a small leak test fails