2005 CADILLAC STS check engine

Your vehicle may be equipped with front compartment
underhood sight shields, which surround the vehicle’s
engine cover. These sight shields will need to be
removed in order to access some of the underhood
components in your vehicle.
To remove the sight shields, turn the fasteners on each
shield to the left until they pop out. Then remove the
fasteners and lift the shields up and away from the
shock towers that support them.
After you have removed the sight shields (if equipped)
on the 3.6L V6 engine, here is what you will see:
A. Underhood Fuse Block. SeeUnderhood Fuse Block
on page 5-96.
B. Windshield Washer Fluid Reservoir. See “Adding
Washer Fluid” underWindshield Washer Fluid
on page 5-32.
C. Battery. SeeBattery on page 5-37.D. Passenger Compartment Air Filter. SeePassenger
Compartment Air Filter on page 3-58.
E. Power Steering Fluid Reservoir. SeePower Steering
Fluid on page 5-31.
F. Engine Oil Fill Cap. See “When to Add Engine Oil”
underEngine Oil on page 5-15.
G. Engine Oil Dipstick (Out of View). See “Checking
Engine Oil” underEngine Oil on page 5-15.
H. Brake Master Cylinder Reservoir. See “Brake Fluid”
underBrakes on page 5-34.
I. Engine Coolant Surge Tank and Pressure Cap. See
Coolant Surge Tank Pressure Cap on page 5-24
andCooling System on page 5-27.
J. Engine Air Cleaner/Filter. SeeEngine Air
Cleaner/Filter on page 5-20.
5-13

After you have removed the sight shields (if equipped)
on the 4.6L V8 engine, here is what you will see:
A. Underhood Fuse Block. SeeUnderhood Fuse Block
on page 5-96.
B. Battery. SeeBattery on page 5-37.
C. Passenger Compartment Air Filter. SeePassenger
Compartment Air Filter on page 3-58.
D. Windshield Washer Fluid Reservoir. See “Adding
Washer Fluid” underWindshield Washer Fluid
on page 5-32.
E. Power Steering Fluid Reservoir. SeePower Steering
Fluid on page 5-31.
F. Engine Oil Fill Cap. See “When to Add Engine Oil”
underEngine Oil on page 5-15.
G. Engine Oil Dipstick (Out of View). See “Checking
Engine Oil” underEngine Oil on page 5-15.
H. Brake Master Cylinder Reservoir. See “Brake Fluid”
underBrakes on page 5-34.
I. Engine Coolant Surge Tank and Pressure Cap. See
Coolant Surge Tank Pressure Cap on page 5-24
andCooling System on page 5-27.
J. Engine Air Cleaner/Filter. SeeEngine Air
Cleaner/Filter on page 5-20.If your vehicle is equipped with front compartment
underhood sight shields, before closing the hood be sure
to replace the sight shields. To replace the shields,
locate the ribs on the underside of each shield and guide
the ribs on to the supporting shock towers. Then
insert the fasteners into the top of the shield and push
the fasteners back into place.
Engine Oil
Checking Engine Oil
It is a good idea to check your engine oil every time you
get fuel. In order to get an accurate reading, the oil
must be warm and the vehicle must be on level ground.
The engine oil dipstick handle is a yellow loop. See
Engine Compartment Overview on page 5-12for
the location of the engine oil dipstick.
1. Turn off the engine and give the oil several minutes
to drain back into the oil pan. If you do not do this,
the oil dipstick might not show the actual level.
2. Pull out the dipstick and clean it with a paper towel
or cloth, then push it back in all the way. Remove it
again, keeping the tip down, and check the level.
5-15

Your vehicle’s engine is lled at the factory with a
Mobil 1®synthetic oil, which meets all requirements for
your vehicle.
Substitute Engine Oil: When adding oil to maintain
engine oil level, oil meeting GM Standard GM4718M
may not be available. You can add substitute oil
designated SAE 5W-30 with the starburst symbol at all
temperatures. Substitute oil not meeting GM Standard
GM4718M should not be used for an oil change.
Engine Oil Additives
Do not add anything to your oil. The recommended oils
with the starburst symbol that meet GM Standard
GM4718M are all you will need for good performance
and engine protection.
Engine Oil Life System
When to Change Engine Oil
Your vehicle has a computer system that lets you know
when to change the engine oil and lter. This is based on
engine revolutions and engine temperature, and not on
mileage. Based on driving conditions, the mileage at
which an oil change will be indicated can vary
considerably. For the oil life system to work properly, you
must reset the system every time the oil is changed.When the system has calculated that oil life has been
diminished, it will indicate that an oil change is
necessary. A CHANGE ENGINE OIL SOON message in
the DIC will come on. SeeDIC Warnings and Messages
on page 3-78. Change your oil as soon as possible
within the next 600 miles (1 000 km). It is possible that,
if you are driving under the best conditions, the oil
life system may not indicate that an oil change is
necessary for over a year. However, your engine oil and
lter must be changed at least once a year and at
this time the system must be reset. Your dealer has
GM-trained service people who will perform this
work using genuine GM parts and reset the system. It is
also important to check your oil regularly and keep it
at the proper level.
If the system is ever reset accidentally, you must
change your oil at 3,000 miles (5 000 km) since your
last oil change. Remember to reset the oil life system
whenever the oil is changed.
5-18

3. Loosen the clamp and remove the duct from the
passenger’s side of the engine air cleaner/lter.
4. The two sides of the airbox are hinged at the
bottom. Open the airbox by pushing the top of
the airbox cover toward the engine.
5. Remove the air lter by lifting it straight up through
the opening in the airbox.
6. Inspect or replace the engine air cleaner/lter. See
Normal Maintenance Replacement Parts on
page 6-14for the correct part number for the lter.
7. Reinstall the cover by reversing Steps 1 through 4.
{CAUTION:
Operating the engine with the air cleaner/lter
off can cause you or others to be burned.
The air cleaner not only cleans the air; it helps
to stop ame if the engine backres. If it is not
there and the engine backres, you could be
burned. Do not drive with it off, and be careful
working on the engine with the air
cleaner/lter off.Notice:If the air cleaner/lter is off, a backre can
cause a damaging engine re. And, dirt can
easily get into your engine, which will damage it.
Always have the air cleaner/lter in place when you
are driving.
Automatic Transmission Fluid
It is not necessary to check the transmission uid level.
A transmission uid leak is the only reason for uid
loss. If a leak occurs, take your vehicle to the dealership
service department and have it repaired as soon as
possible.
Change the uid and lter at the intervals listed in
Additional Required Services on page 6-6, and be sure
to use the transmission uid listed inRecommended
Fluids and Lubricants on page 6-12.
Notice:Use of the incorrect automatic transmission
uid may damage your vehicle, and the damages
may not be covered by your warranty. Always
use the automatic transmission uid listed in
Recommended Fluids and Lubricants on page 6-12.
5-21

If you have to add coolant more than once or twice a
year, have your dealer check your cooling system.
Notice:If you use the proper coolant, you do not
have to add extra inhibitors or additives which claim
to improve the system. These can be harmful.
Checking Coolant
The coolant surge tank and pressure cap are located on
the driver’s side of the vehicle, toward the rear of the
engine compartment. SeeEngine Compartment
Overview on page 5-12for more information on location.
{CAUTION:
Turning the surge tank pressure cap when the
engine and radiator are hot can allow steam
and scalding liquids to blow out and burn you
badly. Never turn the surge tank pressure
cap — even a little — when the engine and
radiator are hot.
The vehicle must be on a level surface. When your
engine is cold, the coolant level should be at the FULL
COLD/FROID line on the side of the surge tank.
Follow the arrow from the top of the tank down the side
to the horizontal mark.
If the Check Coolant Level message in the Driver
Information Center (DIC) comes on and stays on,
it means you are low on engine coolant. See
DIC Warnings and Messages on page 3-78
for more information.
5-23

If Steam Is Coming From Your Engine
{CAUTION:
Steam from an overheated engine can burn
you badly, even if you just open the hood. Stay
away from the engine if you see or hear steam
coming from it. Just turn it off and get
everyone away from the vehicle until it cools
down. Wait until there is no sign of steam or
coolant before you open the hood.
If you keep driving when your engine is
overheated, the liquids in it can catch re.
You or others could be badly burned. Stop
your engine if it overheats, and get out of the
vehicle until the engine is cool.
SeeOverheated Engine Protection Operating
Mode on page 5-26for information on driving
to a safe place in an emergency.Notice:If your engine catches re because you keep
driving with no coolant, your vehicle can be badly
damaged. The costly repairs would not be covered by
your warranty. SeeOverheated Engine Protection
Operating Mode on page 5-26for information on
driving to a safe place in an emergency.If No Steam Is Coming From Your
Engine
An overheat warning, along with a Check Coolant Level
message, can indicate a serious problem.
If you get an engine overheat warning with no Check
Coolant Level message, but see or hear no steam, the
problem may not be too serious. Sometimes the
engine can get a little too hot when you:
Climb a long hill on a hot day.
Stop after high-speed driving.
Idle for long periods in traffic.
Tow a trailer.
5-25

When the engine is cold, the coolant level should be at
or slightly above the FULL COLD/FROID line on the
side of the coolant surge tank. If it is not, you may have
a leak at the pressure cap or in the radiator hoses,
heater hoses, radiator, water pump or somewhere else
in the cooling system.
{CAUTION:
Heater and radiator hoses, and other engine
parts, can be very hot. Do not touch them. If
you do, you can be burned.
Do not run the engine if there is a leak. If you
run the engine, it could lose all coolant. That
could cause an engine re, and you could be
burned. Get any leak xed before you drive the
vehicle.
If there seems to be no leak, with the engine on, check
to see if the electric engine cooling fans are running.
If the engine is overheating, both fans should be
running. If they are not, your vehicle needs service.Notice:Engine damage from running your engine
without coolant is not covered by your warranty. See
Overheated Engine Protection Operating Mode on
page 5-26for information on driving to a safe place
in an emergency.
Notice:Using coolant other than DEX-COOL
®may
cause premature engine, heater core or radiator
corrosion. In addition, the engine coolant may
require changing sooner, at 30,000 miles (50 000 km)
or 24 months, whichever occurs rst. Any repairs
would not be covered by your warranty. Always use
DEX-COOL
®(silicate-free) coolant in your vehicle.
How to Add Coolant to the Coolant
Surge Tank
If you have not found a problem yet, check to see if
coolant is visible in the surge tank. If coolant is visible
but the coolant level is not at the FULL COLD/FROID
line on the side of the coolant surge tank, add a
50/50 mixture ofclean, drinkable waterand DEX-COOL
®
coolant at the coolant surge tank, but be sure the
cooling system, including the coolant surge tank
pressure cap, is cool before you do it. SeeEngine
Coolant on page 5-22for more information.
5-28

4. With the coolant surge tank pressure cap off, start
the engine and let it run until you can feel the upper
radiator hose getting hot. The upper radiator
hose is the largest of the hoses which comes out of
the radiator, on the passenger’s side of the
vehicle. Watch out for the engine cooling fans.
By this time, the coolant level inside the coolant
surge tank may be lower. If the level is lower, add
more of the proper mixture to the coolant surge tank
until the level reaches the FULL COLD/FROID
line on the side of the coolant surge tank.
5. Then replace the pressure cap. Be sure the
pressure cap is hand-tight and fully seated.
Start the engine and allow it to warm up. If the Check
Coolant Level message does not appear on the
Driver Information Center, the coolant is at the proper ll
level. If a Check Coolant Level message does appear,
repeat Steps 1 to 3 then reinstall the pressure cap,
or see your GM dealer.Power Steering Fluid
The power steering uid
reservoir is located in the
center of the engine
compartment, toward the
front of the vehicle.
SeeEngine Compartment
Overview on page 5-12
for more information
on location.
When to Check Power Steering Fluid
It is not necessary to regularly check power steering uid
unless you suspect there is a leak in the system or
you hear an unusual noise. A uid loss in this system
could indicate a problem. Have the system inspected
and repaired.
5-31