ignition GMC SIERRA 1999 Service Manual

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3-20
REV (4): Press and hold REV to return rapidly to a
favorite passage. You will hear the disc selection play at
high speed while you press the REV button. This allows
you to listen and find out when the disc is at the desired
selection. Release REV to resume playing.
FWD (6): Press and hold this button to advance rapidly
within a track. You will hear the disc selection play at
high speed while you press the FWD button. This allows
you to listen and find out when the disc is at the desired
selection. Release FWD to resume playing.
RECALL: Press this button to see what track is playing.
Press it again within five seconds to see how long the
CD has been playing that track. Elapsed time is
displayed in minutes and tenths of a second. The track
number will also appear when a new track begins to
play. Press RECALL again to return to the time display.
AM
-FM: While in the CD mode, press this button to
stop playing the CD and play the radio. The CD symbol
will still display but the word CD will be replaced with
either AM, FM1 or FM2. (If the radio is turned off, the
disc stays in the player and will resume playing at the
point where it stopped.)CD AUX: To switch between the player and the radio
when a disc is playing, press the AM
-FM button. To
return to the player, press CD AUX. When a disc is
playing, the letters CD and the CD symbol will appear
on the display. (If the radio is turned off, the disc stays
in the player and will resume playing at the point where
it stopped.)
EJECT: Press this button to eject the disc from the
player and play the radio. When the same or a new disc
is inserted, the disc will start playing on track one. If a
compact disc is left sitting in the opening for more than
a few seconds, the player will pull the CD back in. The
radio will continue playing. When the ignition is off,
press this button to load a CD.

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3-21 Remote Compact Disc Player (If Equipped)
If you have this option, you can play one compact disc
(CD) at a time.
To load a CD into the player, hold the disc with the label
side up and insert it carefully into the player
(approximately halfway). The disc will automatically be
pulled into the player. If the radio is off and the ignition
is on when a CD is inserted, the radio will turn on and
begin playing the CD. It is possible to load and unload
CDs with the ignition off. To load a disc with the
ignition off, press the EJECT button on the remote
player and then insert the disc. To remove the disc, press
the EJECT button and remove the disc from the player.
A disc that has been ejected but is still sitting in the
remote CD player will be pulled back into the player
after approximately 30 seconds. This protects the disc
and player from damage. The disc will not start playing.To remove the disc, press the EJECT button and remove
the disc from the player.
All of the compact disc functions are controlled by the
radio buttons except for EJECT. When a disc is in the
player, a CD symbol will appear on the display. When a
disc is playing, the letters CD will appear next to the
CD symbol in the bottom left corner. The track number
will also be displayed.
If the disc comes back out and ERR appears on the
display, it could be that:

The disc is upside down.

It is dirty, scratched or wet.

There's too much moisture in the air. (Wait about an
hour and try again.)

You are driving on a very rough road.
Please contact your dealership if any error recurs or
cannot be corrected.
PREV (1): Press this button to go back to the start of the
current track if more than eight seconds have played.
Press PREV again to go to the previous track on the disc.

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3-23
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.
NOTE: 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.
Unlocking the Theft
-Deterrent Feature After a
Power Loss
Enter your secret code as follows; pause no more than
15 seconds between steps:
1. Turn the ignition on. LOC will appear on the display.
2. Press MN and 000 will appear on the display.
3. Press MN again to make the last two digits agree
with your code.
4. Press HR to make the first one or two digits agree
with your code.
5. Press AM
-FM after you have confirmed that the
code matches the secret code you have written down.
The display will show SEC, indicating the radio is
now operable and secure.

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3-24
If you enter the wrong code eight times, INOP will
appear on the display. You will have to wait an hour
with the ignition on before you can try again. When you
try again, you will only have three chances to enter the
correct code before INOP appears.
If you lose or forget your code, contact your dealer.
Disabling the Theft
-Deterrent Feature
Enter your secret code as follows; pause no more than
15 seconds between steps:
1. Turn the ignition to ACCESSORY or RUN.
2. Turn the radio off.
3. Press the 1 and 4 buttons together. Hold them down
until SEC shows on the display.
4. Press MN and 000 will appear on the display.
5. Press MN again to make the last two digits agree
with your code.
6. Press HR to make the first one or two digits agree
with your code.
7. Press AM
-FM after you have confirmed that the
code matches the secret code you have written down.
The display will show
---, indicating that the radio is
no longer secured.If the code entered is incorrect, SEC will appear on the
display. The radio will remain secured until the correct
code is entered.
When battery power is removed and later applied to a
secured radio, the radio won't turn on and LOC will
appear on the display.
To unlock a secured radio, see ªUnlocking the
Theft
-Deterrent Feature After a Power Lossº earlier in
this section.
Understanding Radio Reception
AM
The range for most AM stations is greater than for FM,
especially at night. The longer range, however, can
cause stations to interfere with each other. AM can pick
up noise from things like storms and power lines. Try
reducing the treble to reduce this noise if you ever get it.
FM Stereo
FM stereo will give you the best sound, but FM signals
will reach only about 10 to 40 miles (16 to 65 km). Tall
buildings or hills can interfere with FM signals, causing
the sound to come and go.

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3-26 Care of Your Cassette Tape Player
A tape player that is not cleaned regularly can cause
reduced sound quality, ruined cassettes or a damaged
mechanism. Cassette tapes should be stored in their
cases away from contaminants, direct sunlight and
extreme heat. If they aren't, they may not operate
properly or may cause failure of the tape player.
Your tape player should be cleaned regularly after every
50 hours of use. Your radio may display CLN to indicate
that you have used your tape player for 50 hours without
resetting the tape clean timer. If this message appears on
the display, your cassette tape player needs to be
cleaned. It will still play tapes, but you should clean it as
soon as possible to prevent damage to your tapes and
player. If you notice a reduction in sound quality, try a
known good cassette to see if it is the tape or the tape
player at fault. If this other cassette has no improvement
in sound quality, clean the tape player.
The recommended cleaning method for your cassette
tape player is the use of a scrubbing action,
non
-abrasive cleaning cassette with pads which scrub
the tape head as the hubs of the cleaner cassette turn.
The recommended cleaning cassette is available through
your dealership (GM Part No. 12344789).When using a scrubbing action, non
-abrasive cleaning
cassette, it is normal for the cassette to eject because
your unit is equipped with a cut tape detection feature
and a cleaning cassette may appear as a broken tape.
To prevent the cleaning cassette from being ejected, use
the following steps.
If your vehicle is equipped with the AM
-FM Stereo with
Cassette Tape Player:
1. Turn the ignition to RUN or ACCESSORY.
2. Turn the radio on.
3. Insert the scrubbing action cleaning cassette.
4. Within five seconds, press and hold the REV and
FWD buttons at the same time for three seconds. The
tape symbol on the display will flash, showing that
the cut tape detection feature is no longer active.
5. Eject the cleaning cassette after the manufacturer's
recommended cleaning time.
If your vehicle is equipped with the AM
-FM Stereo with
Cassette Tape Player and Automatic Tone Control:
1. Turn the ignition to RUN or ACCESSORY.
2. Turn the radio off.

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4-26 Driving in Water
Light rain causes no special off-road driving problems.
But heavy rain can mean flash flooding, and flood
waters demand extreme caution.
Find out how deep the water is before you drive through
it. If it's deep enough to cover your wheel hubs, axles or
exhaust pipe, don't try it
-- you probably won't get
through. Also, water that deep can damage your axle
and other vehicle parts.
If the water isn't too deep, then drive through it slowly.
At fast speeds, water splashes on your ignition system
and your vehicle can stall. Stalling can also occur if you
get your tailpipe under water. And, as long as your
tailpipe is under water, you'll never be able to start your
engine. When you go through water, remember that when
your brakes get wet, it may take you longer to stop.
CAUTION:
Driving through rushing water can be dangerous.
Deep water can sweep your vehicle downstream
and you and your passengers could drown. If it's
only shallow water, it can still wash away the
ground from under your tires, and you could lose
traction and roll the vehicle over. Don't drive
through rushing water.
See ªDriving Through Waterº in the Index for more
information on driving through water.
After Off-Road Driving
Remove any brush or debris that has collected on the
underbody, chassis or under the hood. These
accumulations can be a fire hazard.
After operation in mud or sand, have the brake linings
cleaned and checked. These substances can cause
glazing and uneven braking. Check the body structure,
steering, suspension, wheels, tires and exhaust system
for damage. Also, check the fuel lines and cooling
system for any leakage.

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4-35

Keep your vehicle in good shape. Check all fluid
levels and also the brakes, tires, cooling system and
transmission. These parts can work hard on
mountain roads.

Know how to go down hills. The most important
thing to know is this: let your engine do some of the
slowing down. Shift to a lower gear when you go
down a steep or long hill.
CAUTION:
If you don't shift down, your brakes could get so
hot that they wouldn't work well. You would then
have poor braking or even none going down a hill.
You could crash. Shift down to let your engine
assist your brakes on a steep downhill slope.
CAUTION:
Coasting downhill in NEUTRAL (N) or with the
ignition off is dangerous. Your brakes will have to
do all the work of slowing down. They could get so
hot that they wouldn't work well. You would then
have poor braking or even none going down a hill.
You could crash. Always have your engine running
and your vehicle in gear when you go downhill.

Know how to go uphill. You may want to shift down
to a lower gear. The lower gears help cool your engine
and transmission, and you can climb the hill better.

Stay in your own lane when driving on two
-lane
roads in hills or mountains. Don't swing wide or cut
across the center of the road. Drive at speeds that let
you stay in your own lane.

As you go over the top of a hill, be alert. There could be
something in your lane, like a stalled car or an accident.

You may see highway signs on mountains that warn of
special problems. Examples are long grades, passing or
no
-passing zones, a falling rocks area or winding
roads. Be alert to these and take appropriate action.

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4-42 Four-Wheel-Drive Vehicles
CAUTION:
Shifting the transfer case into NEUTRAL (N) can
cause your vehicle to roll even if the transmission
is in PARK (P), for an automatic transmission, or
if your vehicle is in gear, for a manual
transmission. You or others could be injured.
Make sure the parking brake is firmly set before
you shift the transfer case into NEUTRAL (N).
Vehicles equipped with the electronic transfer case
cannot be towed with all four wheels on the ground.
Use the following procedure to correctly tow your
vehicle on all four wheels with a manual transfer case:
1. Firmly set the parking brake.
2. Place the transmission in PARK (P) or a manual
transmission in FIRST (1).
3. Securely attach the vehicle being towed to the
tow vehicle.
4. With the engine running, shift the transfer case to
NEUTRAL (N). See ªFour
-Wheel Driveº in the
Index for the proper procedure to select the neutral
position for your vehicle.
5. Release the parking brake only after the vehicle
being towed is firmly attached to the towing vehicle.
6. Turn the ignition to OFF. The OFF position unlocks
the steering column and reduces battery drain.
Unlocking the steering column will allow the proper
movement of the front wheels and tires during towing.

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4-63 Using a Transfer Case Mounted Power
Take-Off (Automatic Transmission)
1. Set the parking brake.
2. Turn the ignition off.
3. Shift the transfer case into NEUTRAL (N).
4. Shift the transmission into NEUTRAL (N).
5. Engage the PTO.
If you are going to drive the vehicle, shift the
transfer case into the range you want. Turn the
ignition to START. Then apply the regular brakes
and release the parking brake.
6. Shift the transmission to THIRD (3) to start the PTO.
7. Release the regular brakes to drive the vehicle.
Disengaging a Power Take-Off
1. Turn the ignition off.
2. Put the transmission in PARK (P).
3. Release the PTO
4. Restart the engine.
Step-Bumper Pad
If your vehicle has a rear step bumper, it may
be equipped with a rear step pad at the center of
the bumper.
If you will be using the
bumper to tow a trailer, you
must remove the center
cutout circle to install the
trailer ball. You must
also remove both outer
cutouts to attach the
trailer safety chains.
To remove the pad, lift the
edge of the pad from the
rear of the bumper and
swing it forward. When the
pad releases from the
bumper holes, lift the
pad off.

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5-4
2. Get the vehicles close enough so the jumper cables
can reach, but be sure the vehicles aren't touching
each other. If they are, it could cause a ground
connection you don't want. You wouldn't be able to
start your vehicle, and the bad grounding could
damage the electrical systems.
To avoid the possibility of the vehicles rolling, set
the parking brake firmly on both vehicles involved in
the jump start procedure. Put an automatic
transmission in PARK (P) or a manual transmission
in NEUTRAL (N). If you have a four
-wheel-drive
vehicle, be sure the transfer case is not in
NEUTRAL (N).
3. Turn off the ignition on both vehicles. Unplug
unnecessary accessories plugged into the cigarette
lighter or accessory power outlets. Turn off all lamps
that aren't needed as well as radios. This will avoid
sparks and help save both batteries. In addition, it
could save your radio!
NOTICE:
If you leave your radio on, it could be badly
damaged. The repairs wouldn't be covered by
your warranty.
4. Open the hoods and locate the batteries. Find the
positive (+) and negative (
-) terminals on each battery.
CAUTION:
If your vehicle has air conditioning, the auxiliary
electric fan under the hood can start up even
when the engine is not running and can injure
you. Keep hands, clothing and tools away from
any underhood electric fan.