government emission standards. The OBD-II system also assists your
authorized dealer in properly servicing your vehicle. When theService
engine soon
indicator illuminates, the OBD-II system has detected
a malfunction. Temporary malfunctions may cause theService engine
soon
indicator to illuminate. Examples are:
1. The vehicle has run out of fuel—the engine may misfire or run poorly.
2. Poor fuel quality or water in the fuel—the engine may misfire or run
poorly.
3. The fuel cap may not have been securely tightened. SeeFuel filler
capin this chapter.
4. Driving through deep water—the electrical system may be wet.
These temporary malfunctions can be corrected by filling the fuel tank
with good quality fuel, properly tightening the fuel cap or letting the
electrical system dry out. After three driving cycles without these or any
other temporary malfunctions present, theService engine soon
indicator should stay off the next time the engine is started. A driving
cycle consists of a cold engine startup followed by mixed city/highway
driving. No additional vehicle service is required.
If theService engine soon
indicator remains on, have your vehicle
serviced at the first available opportunity. Although some malfunctions
detected by the OBD-II may not have symptoms that are apparent,
continued driving with theService engine soon
indicator on can
result in increased emissions, lower fuel economy, reduced engine and
transmission smoothness, and lead to more costly repairs.
Readiness for Inspection/Maintenance (I/M) testing
Some state/provincial and local governments may have
Inspection/Maintenance (I/M) programs to inspect the emission control
equipment on your vehicle. Failure to pass this inspection could prevent
you from getting a vehicle registration. Your vehicle may not pass the I/M
test if theService engine soon
indicator is on or not working
properly (bulb is burned out), or if the OBD-II system has determined
that some of the emission control systems have not been properly
checked. In this case, the vehicle is considered not ready for I/M testing.
If theService engine soon
indicator is on or the bulb does not
work, the vehicle may need to be serviced. Refer to the On board
diagnostics (OBD-II) description in this chapter.
If the vehicle’s engine or transmission has just been serviced, or the
battery has recently run down or been replaced, the OBD-II system may
2009 05+ Mustang(197)
Owners Guide
USA(fus)
Maintenance and Specifications
272
