Service Engine Soon; Light Turns On Solid - Ford 1998 Mustang Owner's Manual

Instrumentation

Service engine soon

Your vehicle is
SERVICE
ENGINE
equipped with a
SOON
computer that monitors
the engine's emission
control system. This
system is commonly known as the On Board
Diagnostics System (OBD II). The OBD II system
protects the environment by ensuring that your
vehicle continues to meet government emission
standards. The OBD II system also assists the
service technician in properly servicing your vehicle.
The Service Engine Soon indicator light illuminates
when the ignition is first turned to the ON position
to check the bulb. If it comes on after the engine is
started, one of the engine's emission control systems
may be malfunctioning. The light may illuminate
without a driveability concern being noted. The
vehicle will usually be drivable and will not require
towing.
What you should do if the Service Engine Soon
light illuminates

Light turns on solid:

This means that the OBD II system has detected a
malfunction.
Temporary malfunctions may cause your Service
Engine Soon light 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.
3. The fuel cap may not have been properly installed
and securely tightened.
These temporary malfunctions can be corrected by
filling the fuel tank with good quality fuel and/or
properly installing and securely tightening the gas
cap. After three driving cycles without these or any
other temporary malfunctions present, the Service
Engine Soon light should turn off. (A driving cycle
8