OBD port Mercury Grand Marquis 1999 Owner's Manuals

Check engine
Your vehicle is equipped with a
computer that monitors the engine's
emission control system. This
system is commonly known as the
On Board Diagnostics System (OBD
II). This 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.
TheCheck Engineindicator 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 check engine light illuminates
Light turns on solid:
This means that the OBD II system has detected a malfunction.
Temporary malfunctions may cause yourCheck Enginelight 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, theCheck Enginelight should turn off.
(A driving cycle consists of a cold engine startup followed by mixed
city/highway driving.) No additional vehicle service is required.
If theCheck Enginelight remains on, have your vehicle serviced at the
first available opportunity.
CHECK
ENGINE
Instrumentation
7