GMC Sierra Owners Manual
Fuel System Messages
FUEL LEVEL LOW
This message displays and a chime may sound if the fuel level is low.
Refuel as soon as possible. See Fuel Gauge on page 5‑15 and Fuel on page 9‑73 for more information.
TIGHTEN GAS CAP
This message may display along with the check engine light on the instrument panel cluster if the vehicle's fuel cap is not tightened properly. See Malfunction Indicator Lamp on page 5‑25. Reinstall the fuel cap fully. See Filling the Tank on page 9‑77. The diagnostic system can determine if the fuel cap has been left off or improperly installed. A loose or missing fuel cap allows fuel to evaporate into the atmosphere. A few driving trips with the cap properly installed should turn this light and message off.