
The 2003 GMC  Sierra Denali Owner  Manual a 
Seats  and  Restraint  Systems ........................... 1-1 
Front  Seats ............................................... 1-2 
Rear  Seats 
............................................... 1-7 
Safety  Belts 
.............................................. 1-8 
Child  Restraints 
....................................... 1-30 
Air  Bag  Systems 
...................................... 1-57 
Restraint  System  Check 
............................ 1-73 
Features  and  Controls 
..................................... 2-1 
Keys 
........................................................ 2-2 
Doors  and  Locks 
....................................... 2-6 
Windows 
................................................. 2-1 0 
Theft-Deterrent  Systems ............................ 2-1 3 
Starting  and Operating Your Vehicle ........... 2-15 
Mirrors 
.................................................... 2-28 
Onstar@  System 
...................................... 2-33 
HomeLink@  Transmitter 
............................. 2-35 
Storage  Areas 
......................................... 2-39 
Instrument  Panel 
............................................. 3-1 
Vehicle 
Personalization 
............................. 2-42 
Instrument  Panel  Overview 
.......................... 3-2 
Climate  Controls 
...................................... 3-1 8 
Warning  Lights,  Gages  and  Indicators 
......... 3-24 
Driver Information Center  (DIC) 
.................. 3-43 
Audio  System(s) 
....................................... 3-61  Driving  Your  Vehicle 
....................................... 4-1 
Your 
Driving, the  Road, and Your  Vehicle ..... 4-2 
Towing 
................................................... 4-45 
Service  and Appearance Care 
.......................... 5-1 
Service 
..................................................... 5-3 
Fuel 
......................................................... 5-5 
Checking  Things  Under  the  Hood 
............................................. 5-10 
All-Wheel  Drive 
........................................ 5-49 
Rear  Axle 
............................................... 5-50 
Front Axle 
............................................... 5-51 
Bulb  Replacement 
.................................... 5-52 
Windshield  Wiper Blade Replacement 
......... 5-60 
Tires 
...................................................... 5-61 
Appearance  Care 
..................................... 5-86 
Vehicle  Identification 
................................. 5-94 
Electrical  System 
...................................... 5-95 
Capacities  and Specifications 
................... 5-1 04 
Normal  Maintenance  Replacement  Parts 
.... 5-1 05 
Maintenance  Schedule 
..................................... 6-1 
Maintenance  Schedule 
................................ 6-2 
Customer Assistance  Information 
.................... 7-1 
Customer  Assistance  Information 
.................. 7-2 
Reporting Safety  Defects 
............................ 7-9 
Index 
................................................................. 1  

If the  water  isn’t  too deep,  drive slowly through  it.  At 
faster  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 
+- stop. 
,,jving  thr,,gh  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 
water. 
~ vehicle  over.  Don’t  drive through rushing 
I 
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. 
Your  vehicle will  require  more  frequent  service  due 
to 
off-road use.  Refer  to the  Maintenance  Schedule 
for  additional  information. 
See 
Driving  in  Rain  and on Wet Roads on page 4-30 for 
more  information  on driving through  water. 
4-28  

Towing a Trailer 
If you  don’t  ,se the correct eq-., ...__. t and 
drive  properly,  you  can  lose  control  when  you 
pull  a  trailer.  For  example, 
if the  trailer is too 
heavy,  the  brakes  may not  work  well 
-- or  even 
at  all.  You  and  your  passengers  could  be 
seriously  injured. 
Pull a  trailer  only  if  you  have 
followed  all  the  steps  in  this  section. 
Ask your 
dealer  for  advice  and  information  about  towing 
a  trailer  with  your  vehicle. 
Notice: Pulling  a  trailer  improperly  can  damage 
your  vehicle  and  result  in  costly  repairs  not  covered 
by  your  warranty. 
To pull  a  trailer  correctly,  follow 
the  advice  in  this  part, and see your  dealer  for 
important  information  about  towing  a  trailer  with 
your  vehicle.  Additional  rear  axle  maintenance  is  required  for  a  vehicle  used  to  tow  a  trailer.  See 
“Scheduled  Maintenance  Services”  in  the Index. 
To  identify  the vehicle  trailering capacity  of your vehicle, 
you  should read the information  in “Weight  of the 
Trailer”  that  appears  later in this section. 
If yours  was built with trailering options, as  many are, 
it’s  ready  for heavier trailers.  But trailering  is different 
than just  driving  your vehicle  by itself. Trailering  means 
changes  in handling, durability  and fuel  economy. 
Successful, safe trailering takes correct equipment, and  it  has  to be  used  properly. 
That’s the reason for this  part. In it are  many  time-tested, 
important trailering tips  and safety  rules.  Many  of 
these are important  for  your safety and that  of your 
passengers. 
So please read this section carefully before 
you  pull a trailer. 
If You Do  Decide  To Pull A Trailer 
If you  do,  here are  some important points: 
e 
There  are many  different laws, including speed  limit 
restrictions, having  to do  with trailering.  Make sure 
your  rig will  be legal, not only  where  you live 
but also  where you’ll be driving. 
A good  source for 
this  information  can  be state or provincial police. 
Consider  using a  sway  control 
if your trailer  will 
weigh 
5,000 Ibs. (2  270  kg)  or  less.  You  should 
always  use  a  sway  control 
if your trailer will  weigh 
more  than 
5,000 Ibs.  (2  270  kg).  You  can ask  a 
hitch dealer about  sway controls. 
Don’t  tow  a  trailer  at all  during the first 
500 miles 
(800 km)  your  new vehicle is driven.  Your engine, 
axle  or other parts could  be damaged. 
4-5 1  

When You Are  Ready to Leave  After 
Parking  on  a 
Hill 
1. Apply  your  regular  brakes and hold  the pedal  down 
while  you: 
0 start  your  engine, 
shift  into a  gear,  and 
0 release  the  parking brake. 
2. Let  up  on  the  brake  pedal. 
3. Drive slowly  until the trailer  is clear  of the  chocks. 
4. Stop  and  have  someone  pick up  and  store the 
chocks. 
Maintenance  When  Trailer  Towing 
Your vehicle will  need service  more often  when  you’re 
pulling  a trailer.  See the Maintenance  Schedule  for more 
on  this.  Things  that are especially important  in trailer 
operation are automatic transmission  fluid (don’t overfill), 
engine 
oil, axle lubricant, belt, cooling  system and 
brake  system.  Each  of  these  is covered  in  this manual, 
and  the Index will help  you find  them  quickly.  If 
you’re  trailering, it’s  a  good idea to review these sections 
before  you start your trip. 
Check  periodically  to see  that  all hitch nuts and bolts 
are tight. 
4-59  

To replace the engine air cleaner/filter do the following: 
1. Loosen  the  screws  on  the cover of the housing 
and  lift up  the  cover. 
2. Remove  the  air cleaner/filter from  the housing. 
Care  should  be taken 
to dislodge  as little dirt 
as possible. 
3. Clean  the filter sealing surface  and the  housing. 
4. Install the  new engine air cleanedfilter. 
5. Reinstall the cover and tighten the screws.  Refer 
to the  Maintenance  Schedule  to determine  when 
to replace the engine  air cleaner/filter.  See 
Part B: Owner  Checks  and  Services on  page 6-10. 
Operating  the  engine  with  the  air  cleanedfilter 
off can  cause  you  or  others  to  be  burned. The 
air  cleaner  not  only  cleans  the  air, 
it stops 
flame 
if the engine  backfires. If it isn’t  there 
and  the  engine  backfires,  you  could  be  burned.  Don’t  drive  with 
it off, and  be  careful  working 
on  the  engine  with  the  air  cleaner/filter 
off. 
Notice: If  the  air  cleaner/filter  is off, a  backfire 
can  cause  a  damaging  engine  fire.  And, dirt 
can  easily  get  into  your  engine,  which  will  damage 
it. Always  have  the air cleanedfilter  in  place 
when  you’re  driving. 
5-20  

Automatic  Transmission  Fluid 
When to Check and Change 
A good time to  check  your  automatic transmission fluid 
level 
is when  the  engine  oil  is changed. 
Change  both the fluid  and filter every 
50,000 miles 
(83 
000 km) if the vehicle  is mainly  driven under  one  or 
more 
of these  conditions: 
In  heavy  city traffic  where  the outside temperature 
regularly  reaches  90°F  (32°C)  or  higher. 
In hilly or mountainous  terrain. 
When doing frequent trailer  towing. 
Uses  such  as found in taxi,  police  or delivery 
If you  do  not  use  your  vehicle under  any  of these 
conditions,  change  the fluid and filter every 
100,000 miles (1 66 000 km). 
See 
Part A: Scheduled  Maintenance  Services on 
page 
6-4. 
service. 
How to Check 
Because  this operation  can  be a  little difficult,  you  may 
choose  to have  this done  at the dealership service 
department. 
If you  do  it yourself,  be sure  to follow all  the instructions 
here,  or  you  could get  a false reading  on the dipstick. 
Notice: Too much  or too little fluid can damage 
your  transmission.  Too  much  can  mean that  some 
of  the fluid could come  out and fall  on  hot engine 
part 
or exhaust  system parts, starting a fire. 
Too  little fluid could cause the transmission to  overheat.  Be sure  to get  an accurate reading  if you 
check  your transmission fluid. 
Wait  at  least 
30 minutes before checking the 
transmission fluid  level 
if you  have  been  driving: 
0 When outside temperatures are  above  90°F (32°C). 
At high  speed  for  quite a while. 
In  heavy  traffic - especially  in hot weather. 
While  pulling  a trailer. 
To get  the  right  reading, the fluid should  be  at normal 
operating temperature,  which is 180°F 
to 200°F 
(82°C  to 93°C). 
5-2 
1  

Rear Axle 
When to Check  Lubricant 
Refer to the  Maintenance  Schedule  to  determine how 
often to check the  lubricant.  See 
PaHA: Scheduled 
Maintenance Services  on page 
6-4. 
How to Check  Lubricant 
To  get  an accurate  reading,  the vehicle should be on  a 
level  surface.  The 
proper level is  from 
5/8 inch to 1 5/8 inch (1 5 mm  to 
40 mm)  below the  bottom of the  filler  plug hole.  Add 
only  enough fluid to  reach the proper  level.  The  proper 
level  for vehicles with  QUADRASTEERTM 
(4 Wheel 
Steer)  is from 
0 to 1/4 inch (0 to 6 mm)  below  the filler 
plug hole. Add only  enough  fluid  to  reach  the  proper 
level. 
What  to  Use 
Refer to the  Maintenance  Schedule  to determine  what 
kind 
of lubricant to  use.  See Part D: Recommended 
Fluids  and Lubricants  on page 
6- 16. 
5-50  

Front Axle 
When  to  Check Lubricant 
Refer  to the Maintenance  Schedule  to determine  how 
often  to  check  the  lubricant.  See 
Pat? A: Scheduled 
Maintenance  Services  on  page 
6-4. 
How to Check  Lubricant 
To get  an accurate  reading, the vehicle  should be on a 
level  surface. 
If  the  level is  below the bottom 
of the filler  plug  hole, 
you may need to  add  some  lubricant. 
When  the  differential  is cold,  add enough lubricant  to 
raise the  level  to 
0 to 3/8 inch (9.5 mm) below the  filler 
plug hole. 
When  the  differential  is at  operating  temperature 
(warm),  add enough  lubricant  to  raise the  level  to the 
bottom 
of the  filler  plug  hole. 
What  to Use 
Refer  to  the  Maintenance  Schedule  to determine what 
kind  of lubricant  to  use.  See 
Pat? D: Recommended 
Fluids  and Lubricants  on  page 
6-16. 
5-51