Check Engine Warning Light - Ford Ranger Owner's Manual

Check Engine Warning Light

The Powertrain On-Board Diagnostic II (OBD II) system consists
of the hardware and software necessary to monitor the
operation of the powertrain. The OBD II system is designed to
check the function of the vehicle's powertrain control system
during normal operation. If an emission problem is detected, the
Check Engine Warning Light (in the cluster) is turned on.
Modification or additions to the vehicle may cause incorrect
operation of the OBD II system. Additions such as burglar
alarms, cellular phones, and CB radios must be carefully
installed. Do not install these devices by tapping into or running
wires close to powertrain control system wires or components.
The light comes on briefly when you turn the ignition key to
the ON position, but it should turn off when the engine cranks.
If the light does not come on when you turn the ignition to the
ON position or if it comes on and stays on when you are
driving, have your vehicle serviced as soon as conveniently
possible. This indicates a possible problem with one of the
engine's emission control systems. You do not need to have
your vehicle towed in.
If the light turns on and off at one (1) second intervals while
you are driving the vehicle, it means that the engine is
misfiring. If this condition persists, damage could occur to the
engine or catalytic convertor. Have your vehicle serviced at the
first opportunity. You do not need to have your vehicle towed
in.
If the light turns on and off on rare occasions while you are
driving, it means that a malfunction occurred and the condition
corrected itself.
An example of a condition which corrects itself occurs when an
engine running out of fuel begins to misfire. In this case, the
Check Engine Warning Light may turn on and will then set a
Diagnostic Trouble Code indicating that the engine was
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