Cadillac escalade ext 2002 ユーザーズマニュアル

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
the cap. See “Filling Your Tank” in the Index. 
The diagnostic system can determine if the fuel cap 
has been left off or improperly installed. A loose or
missing fuel cap will allow fuel to evaporate into the
atmosphere. A few driving trips with the cap properly
installed should turn the light off.

Did you just drive through a deep puddle of water?

If so, your electrical system may be wet. The condition
will usually be corrected when the electrical system
dries out. A few driving trips should turn the light off.

Have you recently changed brands of fuel?

If so, be sure to fuel your vehicle with quality fuel. 
See “Fuel” in the Index. Poor fuel quality will cause
your engine not to run as efficiently as designed. 
You may notice this as stalling after start

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up, 

stalling when you put the vehicle into gear, misfiring,
hesitation on acceleration or stumbling on acceleration.
(These conditions may go away once the engine is
warmed up.) This will be detected by the system and
cause the light to turn on.

If you experience one or more of these conditions,
change the fuel brand you use. It will require at least 
one full tank of the proper fuel to turn the light off.

If none of the above steps have made the light turn off,
have your dealer or qualified service center check the
vehicle. Your dealer has the proper test equipment and
diagnostic tools to fix any mechanical or electrical
problems that may have developed.