See also:

When to Inspect the Engine Air Cleaner/Filter
Inspect the air cleaner/filter at the Maintenance II intervals and replace it at the first oil change after each 50,000 mile (80 000 km) interval. See Scheduled Maintenance for more information. ...

Radiator Pressure Cap
Notice: If the pressure cap is not tightly installed, coolant loss and possible engine damage may occur. Be sure the cap is properly and tightly secured. ...

If the Light Is On Steady
You may be able to correct the emission system malfunction by considering the following: Did you recently put fuel into your vehicle? If so, reinstall the fuel cap, making sure to fully install ...