2002 GMC SONOMA engine control

iv
Vehicle Damage Warnings
Also, in this book you will find these notices:
NOTICE:
These mean there is something that could damage
your vehicle.
In the notice area, we tell you about something that can
damage your vehicle. Many times, this damage would
not be covered by your warranty, and it could be costly.
But the notice will tell you what to do to help avoid
the damage.
When you read other manuals, you might see
CAUTION and NOTICE warnings in different
colors or in different words.
You'll also see warning labels on your vehicle.
They use the same words, CAUTION or NOTICE.
Vehicle Symbols
Your vehicle may be equipped with components and
labels that use symbols instead of text. Symbols,
used on your vehicle, are shown along with the text
describing the operation or information relating to a
specific component, control, message, gage or indicator.
If you need help figuring out a specific name of a
component, gage or indicator reference the following
topics in the Index:

ªEngine Compartment Overviewº

ªInstrument Panelº

ªComfort Controlsº

ªAudio Systemsº
Also see ªWarning Lights and Gagesº in the Index.

2-27
Make sure the shift lever is fully in PARK (P) before
starting the engine. Your vehicle has an automatic
transmission shift lock control system. You have to fully
apply your regular brakes before you can shift from
PARK (P) when the ignition key is in RUN. If you
cannot shift out of PARK (P), ease pressure on the shift
lever
-- push the shift lever all the way into PARK (P)
as you maintain brake application. Then move the shift
lever into the gear you wish. See ªShifting Out of
PARK (P)º in the Index.
REVERSE (R): Use this gear to back up.
NOTICE:
Shifting to REVERSE (R) while your vehicle
is moving forward could damage your
transmission. Shift to REVERSE (R) only
after your vehicle is stopped.
To rock your vehicle back and forth to get out of snow,
ice or sand without damaging your transmission, see
ªStuck In Sand, Mud, Ice or Snowº in the Index.NEUTRAL (N): In this position, your engine doesn't
connect with the wheels. To restart when you're already
moving, use NEUTRAL (N) only.
CAUTION:
Shifting out of PARK (P) or NEUTRAL (N) while
your engine is ªracingº (running at high speed) is
dangerous. Unless your foot is firmly on the
brake pedal, your vehicle could move very
rapidly. You could lose control and hit people or
objects. Don't shift out of PARK (P) or
NEUTRAL (N) while your engine is racing.
NOTICE:
Damage to your transmission caused by shifting
out of PARK (P) or NEUTRAL (N) with the
engine racing isn't covered by your warranty.

2-31 Shift Speeds
CAUTION:
If you skip a gear when you downshift, you could
lose control of your vehicle. You could injure
yourself or others. Don't shift down more than
one gear at a time when you downshift.
If your vehicle has four-wheel drive and is equipped
with a manual transmission, disregard the SHIFT light
when the transfer case is in 4LO.
Four-Wheel Drive (If Equipped)
If your vehicle has four-wheel drive, you can send your
engine's driving power to all four wheels for extra
traction. To get the most satisfaction out of four
-wheel
drive, you must be familiar with its operation. Read the
part that follows before using four
-wheel drive. You
should use two
-wheel high (2HI) for most normal
driving conditions.
NOTICE:
Driving in the 4HI or 4LO positions for a long
time on dry or wet pavement could shorten the
life of your vehicle's drivetrain.

2-39
Running Your Engine While You're
Parked (Automatic Transmission)
It's better not to park with the engine running. But if you
ever have to, here are some things to know.
CAUTION:
Idling the engine with the climate control system
off could allow dangerous exhaust into your
vehicle. See the earlier Caution under ªEngine
Exhaust.º
Also, idling in a closed-in place can let deadly
carbon monoxide (CO) into your vehicle even
if the fan is at the highest setting. One place
this can happen is a garage. Exhaust
-- with
CO
-- can come in easily. NEVER park in a
garage with the engine running.
Another closed-in place can be a blizzard.
See ªBlizzardº in the Index.
CAUTION:
It can be dangerous to get out of your vehicle if
the shift lever is not fully in PARK (P) with the
parking brake firmly set. Your vehicle can roll.
Don't leave your vehicle when the engine is
running unless you have to. If you've left the
engine running, the vehicle can move suddenly.
You or others could be injured. To be sure your
vehicle won't move, even when you're on fairly
level ground, always set your parking brake and
move the shift lever to PARK (P).
Follow the proper steps to be sure your vehicle won't
move. See ªShifting Into PARK (P)º in the Index.
If you're pulling a trailer, see ªTowing a Trailerº in
the Index.

2-76 Malfunction Indicator Lamp (Service
Engine Soon Light in the United States or
Check Engine Light in Canada)
United States Canada
Your vehicle is equipped with a computer which
monitors operation of the fuel, ignition and emission
control systems.
This system is called OBD II (On
-Board
Diagnostics
-Second Generation) and is intended to assure
that emissions are at acceptable levels for the life of the
vehicle, helping to produce a cleaner environment. The
SERVICE ENGINE SOON or CHECK ENGINE light
comes on to indicate that there is a problem and service is
required. Malfunctions often will be indicated by the
system before any problem is apparent. This may prevent
more serious damage to your vehicle. This system is also
designed to assist your service technician in correctly
diagnosing any malfunction.
NOTICE:
If you keep driving your vehicle with this light
on, after a while, your emission controls may not
work as well, your fuel economy may not be as
good and your engine may not run as smoothly.
This could lead to costly repairs that may not be
covered by your warranty.
NOTICE:
Modifications made to the engine, transmission,
exhaust, intake or fuel system of your vehicle or
the replacement of the original tires with other
than those of the same Tire Performance Criteria
(TPC) can affect your vehicle's emission controls
and may cause the SERVICE ENGINE SOON
OR CHECK ENGINE light to come on.
Modifications to these systems could lead to
costly repairs not covered by your warranty. This
may also result in a failure to pass a required
Emission Inspection/Maintenance test.

2-77
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 Flashing
-- A misfire condition has been
detected. A misfire increases vehicle emissions and
may damage the emission control system on your
vehicle. Dealer or qualified service center diagnosis
and service may be required.

Light On Steady
-- An emission control system
malfunction has been detected on your vehicle.
Dealer or qualified service center 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 flashing and remains on steady, see
ªIf the Light Is On Steadyº following.
If the light continues to flash, 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 flashing,
follow the previous steps, and drive the vehicle to your
dealer or qualified service center for service.

2-79
Emissions Inspection and Maintenance Programs
Some state/provincial and local governments have or
may begin programs to inspect the emission control
equipment on your vehicle. Failure to pass this
inspection could prevent you from getting a vehicle
registration.
Here are some things you need to know in order to help
your vehicle pass an inspection:
Your vehicle will not pass this inspection if the
SERVICE ENGINE SOON or CHECK ENGINE light is
on or not working properly.
Your vehicle will not pass this inspection if the OBD
(on
-board diagnostic) system determines that critical
emission control systems have not been completely
diagnosed by the system. The vehicle would be
considered not ready for inspection. This can happen if
you have recently replaced your battery or if your
battery has run down. The diagnostic system is designed
to evaluate critical emission control systems during
normal driving. This may take several days of routine
driving. If you have done this and your vehicle still does
not pass the inspection for lack of OBD system
readiness, see your dealer or qualified service center to
prepare the vehicle for inspection.
Oil Pressure Gage
United States Canada
The oil pressure gage shows the engine oil pressure
in psi (pounds per square inch) when the engine is
running. Canadian vehicles indicate oil pressure in
kPa (kilopascals).

3-7
Ventilation Tips

Keep the hood and front air inlet free of ice, snow or
any other obstruction (such as leaves). The heater
and defroster will work far better, reducing the
chance of fogging the inside of your windows.

When you enter a vehicle in cold weather, turn the
fan control to high for a few moments before driving
off. This helps clear the intake ducts of snow and
moisture, and reduces the chance of fogging the
inside of your windows.

Keep the air path under the front seats clear of
objects. This helps air to circulate throughout
your vehicle.Audio Systems
Your audio system has been designed to operate easily
and give years of listening pleasure. You will get the
most enjoyment out of it if you acquaint yourself with it
first. Find out what your audio system can do and how
to operate all its controls to be sure you're getting the
most out of the advanced engineering that went into it.
Setting the Clock for Systems with the
SET Button
Press SET. Within five seconds, press and hold the right
SEEK arrow until the correct minute appears on the
display. Press and hold the left SEEK arrow until the
correct hour appears on the display.
Setting the Clock for Systems with HR and
MN Buttons
Press and hold HR until the correct hour appears on the
display. Press and hold MN until the correct minute
appears on the display. To display the clock with the
ignition off, press RECALL or HR/MN and the time
will be displayed for a few seconds. There is an initial
two
-second delay before the clock goes into the
time
-set mode.