ECU GMC SONOMA 1999 User Guide
Page 58 of 381
1-45
CAUTION:
If the air bag readiness light ever comes on when
you have turned off the air bag, it means that
something may be wrong with the air bag system.
The right front passenger's air bag could inflate
even though the switch is off. If this ever
happens, don't let anyone whom the national
government has identified as a member of a
passenger air bag risk group sit in the right front
passenger's position (for example, don't secure a
rear
-facing child restraint in your vehicle) until
you have your vehicle serviced. See ªAIR BAG
OFF Switchº in the Index.
You'll be using the lap-shoulder belt. See the earlier part
about the top strap if the child restraint has one. Be sure
to follow the instructions that came with the child
restraint. Secure the child in the child restraint when and
as the instructions say.
1. Your vehicle has a right front passenger's air bag. If
you are using a rear
-facing child restraint in this seat,
make sure the air bag is turned off. (See ªAIR BAG
OFF Switchº in the Index.) If your child restraint is
forward
-facing, always move the seat as far back as
it will go before securing it in this seat. (See ªSeatsº
in the Index.)
2. Put the restraint on the seat.
3. Pick up the latch plate, and run the lap and shoulder
portions of the vehicle's safety belt through or
around the restraint. The child restraint instructions
will show you how.
If the shoulder belt goes in front of the child's face or
neck, put it behind the child restraint. 
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1-47
6. To tighten the belt, feed the shoulder belt back into the
retractor while you push down on the child restraint. If
you're using a forward
-facing child restraint, you may
find it helpful to use your knee to push down on the
child restraint as you tighten the belt.
7. Push and pull the child restraint in different
directions to be sure it is secure.To remove the child restraint, just unbuckle the vehicle's
safety belt and let it go back all the way. The safety belt
will move freely again and be ready to work for an adult
or larger child passenger.
If you were using a rear
-facing child restraint, turn on
the right front passenger's air bag when you remove the
rear
-facing child restraint from the vehicle unless the
person who will be sitting there is a member of a
passenger air bag risk group. See ªAIR BAG OFF
Switchº in the Index.
CAUTION:
If the right front passenger's air bag is turned off
for a person who isn't in a risk group identified
by the national government, that person won't
have the extra protection of an air bag. In a
crash, the air bag wouldn't be able to inflate and
help protect the person sitting there. Don't turn
off the passenger's air bag unless the person
sitting there is in a risk group. See ªAIR BAG
OFF Switchº in the Index for more on this,
including important safety information. 
Page 71 of 381
2-8
1. Insert a dime in the slot between the covers of the
transmitter housing near the key ring hole. Remove
the bottom by twisting the dime.
2. Remove and replace the battery with a three volt
CR2032 or equivalent battery, positive (+) side up.
3. Align the covers and snap them together.
4. Resynchronize the transmitter.
5. Check the operation of the transmitter.
Resynchronization
Resynchronization may be necessary due to the security
method used by this system. The transmitter does not
send the same signal twice to the receiver. The receiver
will not respond to a signal it has been sent previously.
This prevents anyone from recording and playing back
the signal from the transmitter.
To resynchronize your transmitter, stand close to your
vehicle and press and hold the LOCK and UNLOCK
buttons on the transmitter at the same time for seven
seconds. The door locks should cycle to confirm
synchronization. If the locks do not cycle, see your
dealer for service.
Side Access Panel (Extended Cab) 
(If Equipped)
Your vehicle may be equipped with a side access panel
for convenience in loading and unloading cargo.
To open the side access panel, first open the driver's
front door. Then, use the handle on the panel to open it.
You must close the side access panel before you can
close the driver's door. 
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2-9
Tailgate
You can open the tailgate by pulling up on the handle
while pulling the tailgate down.
When you put the tailgate back up, be sure it 
latches securely.
Follow these steps if you want to remove the tailgate:
1. Raise the tailgate slightly.
2. Remove both retaining
cables. To remove each
cable, turn it so the end
faces the front. Then,
push forward so the
larger part of the hole is
over the bolt. Pull the
end over the bolt.
3. With the tailgate halfway down, pull the tailgate
toward you at the left side and then move the tailgate
to the left to release the right side.
Reverse the procedure to reinstall. Make sure the
tailgate is secure.
Theft
Vehicle theft is big business, especially in some cities.
Although your vehicle has a number of theft
-deterrent
features, we know that nothing we put on it can make it
impossible to steal. However, there are ways you 
can help. 
Page 73 of 381
2-10 Key in the Ignition
If you leave your vehicle with the keys inside, it's an
easy target for joy riders or professional thieves 
-- so
don't do it.
When you park your vehicle and open the driver's door,
you'll hear a chime reminding you to remove your key
from the ignition and take it with you. Always do this.
Your steering wheel will be locked, and so will your
ignition. If you have an automatic transmission, taking
your key out also locks your transmission. Also
remember to lock the doors.
Parking at Night
Park in a lighted spot, close all windows and lock your
vehicle. Remember to keep your valuables out of sight.
Put them in a storage area, or take them with you.
Parking Lots
If you park in a lot where someone will be watching
your vehicle, it's best to lock it up and take your keys.
But what if you have to leave your ignition key? What if
you have to leave something valuable in your vehicle?
Put your valuables in a storage area, like your 
glove box.If your vehicle has a remote keyless entry system,
take the transmitter with you.
Lock all the doors except the driver's.
Content Theft-Deterrent 
(If Equipped)
Your vehicle may be equipped with a Content
Theft
-Deterrent alarm system.
With this system, the
SECURITY light will flash
as you open the door 
(if your ignition is off).
This light reminds you to activate the theft
-deterrent
system. Here's how to do it:
1. Open the door.
2. Lock the door with the power door lock switch or the
remote keyless entry transmitter. The SECURITY
light should come on and stay on. 
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2-11
3. Close all doors. The SECURITY light should go off
after approximately 30 seconds. The alarm is not
armed until the SECURITY light goes off.
If a door is opened without the key or the remote keyless
entry transmitter, the alarm will go off. Your vehicle's
headlamps will flash and the horn will sound for 
110 seconds, then will turn off to save the battery power.
Remember, the theft
-deterrent system won't activate if
you lock the doors with a key or use the manual door
lock. It activates only if you use a power door lock
switch with the door open, or with the remote keyless
entry transmitter. You should also remember that you
can start your vehicle with the correct ignition key if the
alarm has been set off.
Here's how to avoid setting off the alarm by accident:
If you don't want to activate the theft
-deterrent
system, the vehicle should be locked with the door
key after the doors are locked.
Always unlock a door with a key, or use the remote
keyless entry transmitter. Unlocking a door any other
way will set off the alarm.
If you set off the alarm by accident, unlock any door with the 
key. You can also turn off the alarm by pressing UNLOCK on
the remote keyless entry transmitter. The alarm won't stop if 
you try to unlock a door any other way.
Testing the Alarm
The alarm can be tested by following these steps:
1. From inside the vehicle, lower the driver's window
and open the driver's door.
2. Activate the system by locking the doors with the
power door lock switch while the door is open, or
with the remote keyless entry transmitter.
3. Get out of the vehicle, close the door and wait for the
SECURITY light to go out.
4. Then reach in through the window, unlock the door
with the manual door lock and open the door. This
should set off the alarm.
If the alarm does not sound when it should but the
vehicle's headlamps flash, check to see if the horn
works. The horn fuse may be blown. To replace the fuse,
see ªFuses and Circuit Breakersº in the Index.
If the alarm does not sound or the vehicle's headlamps
do not flash, the vehicle should be serviced by an
authorized service center. 
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2-12
Passlock
Your vehicle is equipped with the Passlock
theft
-deterrent system.
Passlock is a passive theft
-deterrent system. Passlock
enables fuel if the ignition lock cylinder is turned with a
valid key. If a correct key is not used or the ignition lock
cylinder is tampered with, fuel is disabled.
During normal operation, the will go off approximately 
five seconds after the key is turned to the 
RUN ignition position.
If the engine stalls and the SECURITY light flashes,
wait about 10 minutes until the light stops flashing
before trying to restart the engine. Remember to release
the key from START as soon as the engine starts.
If the engine does not start after three (3) tries, the
vehicle needs service.
If the engine is running and the SECURITY light comes
on, you will be able to restart the engine if you turn the
engine off. However, your Passlock system is not working
properly and must be serviced by your dealer. Your vehicle
is not protected by Passlock at this time. You may also
want to check the fuse (see ªFuses and Circuit Breakersº
in the Index). See your dealer for service.
In an emergency, call the GM Roadside Assistance
Center. See ªRoadside Assistanceº in the Index.
New Vehicle ªBreak-Inº
NOTICE:
Your vehicle doesn't need an elaborate
ªbreak
-in.º But it will perform better in the long
run if you follow these guidelines:
Keep your speed at 55 mph (88 km/h) or
less for the first 500 miles (805 km).
Don't drive at any one speed 
-- fast or 
slow 
-- for the first 500 miles (805 km). 
Don't make full
-throttle starts.
Avoid making hard stops for the first 
200 miles (322 km) or so. During this time
your new brake linings aren't yet broken
in. Hard stops with new linings can mean
premature wear and earlier replacement.
Follow this breaking
-in guideline every
time you get new brake linings.
Don't tow a trailer during break
-in. 
See ªTowing a Trailerº in the Index for
more information. 
Page 120 of 381
2-57
CAUTION:
If the air bag readiness light ever comes on when
you have turned off the air bag, it means that
something may be wrong with the air bag system.
The right front passenger's air bag could inflate
even though the switch is off. If this ever
happens, don't let anyone whom the national
government has identified as a member of a
passenger air bag risk group sit in the right front
passenger's position (for example, don't secure a
rear
-facing child restraint in your vehicle) until
you have your vehicle serviced.
Charging System Indicator Light
The charging system light
will come on briefly when
you turn on the ignition, but
the engine is not running, as
a check to show you it 
is working.
It should go out once the engine is running. If it stays
on, or comes on while you are driving, you may have a
problem with the charging system. It could indicate that
you have problems with a generator drive belt, or
another electrical problem. Have it checked right away.
Driving while this light is on could drain your battery.
If you must drive a short distance with the light on, be
certain to turn off all your accessories, such as the radio
and air conditioner. 
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2-65 Security Warning Light
This light will come on
briefly when you turn the
key toward START. The
light will stay on until the
engine starts.
If the light flashes, the Passlock
 system has entered a
tamper mode. If the vehicle fails to start, see ªPasslockº
in the Index.
If the light comes on continuously while driving and
stays on, there may be a problem with the Passlock
system. Your vehicle will not be protected by Passlock,
and you should see your dealer.
Also see ªContent Theft
-Deterrentº in the Index for
additional information regarding the SECURITY light.
Service Four-Wheel-Drive Warning Light
If your vehicle is equipped with the Automatic
Four
-Wheel-Drive Transfer Case, it has a computer
which controls the four
-wheel-drive system.
This light should come on
briefly when you turn on the
ignition, as a check to show
you it is working.
The SERVICE 4WD light comes on to indicate that
there may be a problem with the four
-wheel-drive
system and service is required. Malfunctions can be
indicated by the system before any problem is apparent,
which may prevent serious damage to the vehicle. This
system is also designed to assist your service technician
in correctly diagnosing a malfunction. 
Page 151 of 381
3-22 Theft-Deterrent Feature (If Equipped)
THEFTLOCK is designed to discourage theft of your
radio. It works by using a secret code to disable all radio
functions whenever battery power is removed.
The THEFTLOCK feature for the radio may be used or
ignored. If ignored, the system plays normally and the
radio is not protected by the feature. If THEFTLOCK is
activated, your radio will not operate if stolen.
When THEFTLOCK is activated, the radio will display
LOC to indicate a locked condition anytime battery
power has been interrupted. If your battery loses power
for any reason, you must unlock the radio with the secret
code before it will operate.
Activating the Theft
-Deterrent Feature
The instructions which follow explain how to enter your
secret code to activate the THEFTLOCK system. It is
recommended that you read through all nine steps
before starting the procedure.
If you allow more than 15 seconds to elapse between
any steps, the radio automatically reverts to time and
you must start the procedure over at Step 4.1. Write down any three or four
-digit number 
from 000 to 1999 and keep it in a safe place separate
from the vehicle.
2. Turn the ignition to ACCESSORY or RUN.
3. Turn the radio off.
4. Press the 1 and 4 buttons together. Hold them down
until 
--- shows on the display. Next you will use the
secret code number which you have written down.
5. Press MN and 000 will appear on the display.
6. Press MN again to make the last two digits agree
with your code.
7. Press HR to make the first one or two digits agree
with your code.
8. Press AM
-FM after you have confirmed that the
code matches the secret code you have written down.
The display will show REP to let you know that you
need to repeat Steps 5 through 7 to confirm your
secret code.
9. Press AM
-FM and this time the display will show
SEC to let you know that your radio is secure. The
LED indicator by the volume control will begin
flashing when the ignition is turned off.