4 LO flashing GMC ENVOY 2003 Owner's Manual

This light should come on, as a check to show you it is
working, when the ignition is on and the engine is
not running. If the light doesn't come on, have it
repaired. This light will also come on during a
malfunction in one of two ways:
·Light FlashingÐ A mis®re condition has been
detected. A mis®re increases vehicle emissions
and may damage the emission control system on
your vehicle. Diagnosis and service may be
required.
·Light On SteadyÐ An emission control system
malfunction has been detected on your vehicle.
Diagnosis and service may be required.
If the Light Is Flashing
The following may prevent more serious damage to
your vehicle:
·Reducing vehicle speed.
·Avoiding hard accelerations.
·Avoiding steep uphill grades.
·If you are towing a trailer, reduce the amount of
cargo being hauled as soon as it is possible.If the light stops ¯ashing and remains on steady, see ªIf
the Light Is On Steadyº following.
If the light continues to ¯ash, when it is safe to do so,
stop the vehicle.Find a safe place to park your vehicle.
Turn the key off, wait at least 10 seconds and restart
the engine. If the light remains on steady, see ªIf
the Light Is On Steadyº following. If the light is still
¯ashing, follow the previous steps, and see your dealer
for service as soon as possible.
If the Light Is On Steady
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 on page 5-7. 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.
3-43

Gate Operator and Canadian Programming........2-43
Getting Familiar with Off-Road Driving................4-17
Glove Box.....................................................2-44
GM Mobility Program for Persons with
Disabilities.................................................... 7-5
H
Hazard Warning Flashers................................... 3-6
Head Restraints............................................... 1-5
Headlamp High/Low-Beam Changer.................... 3-8
Headlamp Washer..........................................3-11
Headlamps....................................................5-50
Bulb Replacement.......................................5-50
Electrical System.........................................5-89
Front Turn Signal and Sidemarker Lamps.......5-51
Halogen Bulbs............................................5-50
Headphones...................................................3-92
Heated Seats................................................... 1-3
Highway Hypnosis...........................................4-36
Hill and Mountain Roads..................................4-37
Hitches..........................................................4-55
HomeLink Transmitter, Programming..................2-41
HomeLink
žTransmitter....................................2-40
Hood............................................................5-10
Checking Things Under................................5-10
Release.....................................................5-10
Horn............................................................... 3-7How to Add Coolant to the Coolant
Recovery Tank............................................5-31
How to Add Coolant to the Radiator..................5-33
How to Add Fluid............................................5-23
How to Check Lubricant...................................5-48
How to Check Power Steering Fluid..................5-36
How to Check........................................5-22, 5-55
How to Inspect...............................................5-20
How to Use This Manual...................................... ii
How to Wear Safety Belts Properly...................1-14
Hydroplaning..................................................4-31
I
ICE POSSIBLE..............................................3-62
If No Steam Is Coming From Your Engine..........5-28
If Steam Is Coming From Your Engine...............5-27
If the Light Is Flashing.....................................3-43
If the Light Is On Steady.................................3-43
If You Are Stuck in Sand, Mud, Ice or Snow.......4-44
If You Do Decide To Pull A Trailer.....................4-51
If You're Caught in a Blizzard...........................4-41
Ignition Positions.............................................2-19
Ignition Transmission Lock Check......................6-14
Infants and Young Children, Restraints...............1-32
In¯ation -- Tire Pressure..................................5-55
7