2007 Dodge Ram 1500 Pickup Owner's Manual - Page 450

450 MAINTAINING YOUR VEHICLE ONBOARD DIAGNOSTIC SYSTEM (OBD II) Vehicles equipped with California emissions controls have a sophisticated onboard diagnostic system called OBDII. This system monitors the performance of the emissions, engine, and automatic transmission control systems. When these systems are operating properly, your vehicle will provide excellent performance and fuel economy, as well as engine emissions well within current government regulations. If any of these systems require service, the OBD II system will turn on the "Malfunction Indicator Light." It will also store diagnostic codes and other information to assist your service technician in making repairs. Although your vehicle will usually be driveable and not need towing, see your dealer for service as soon as possible. CAUTION! Prolonged driving with the "Malfunction Indicator Light" on could cause further damage to the emission control system. It could also affect fuel economy and driveability. The vehicle must be serviced before any emissions tests can be performed. If the "Malfunction Indicator Light" is flashing, severe catalytic converter damage and power loss will soon occur. Immediate service is required. Loose Fuel Filler Cap Message If the vehicles diagnostic system determines that the fuel filler cap in loose, improperly installed, or damaged, a GASCAP message will be displayed in the instrument cluster. Tighten the gas cap until a "clicking" sound is heard. This is an indication that the gas cap is properly tightened. Press the odometer reset button to turn the