Page 193 of 240

On board diagnostics (OBD-II)
Your vehicle is equipped with a computer that
monitors the engine’s emission control system. This
system is commonly known as the On Board
Diagnostics System (OBD-II). This OBD-II system
protects the environment by ensuring that your
vehicle continues to meet government emission
standards. The OBD-II system also assists the
service technician in properly servicing your vehicle.
When theCheck Engine/Service Engine Soonlight
illuminates, the OBD-II system has detected a
malfunction. Temporary malfunctions may cause
yourCheck Engine/Service Engine Soonlight to
illuminate. Examples are:
1. The vehicle has run out of fuel. (The engine may
misfire or run poorly.)
2. Poor fuel quality or water in the fuel.
3. The fuel cap may not have been securely
tightened.
These temporary malfunctions can be corrected by
filling the fuel tank with good quality fuel and/or
properly tightening the fuel cap. After three driving
cycles without these or any other temporary
malfunctions present, theCheck Engine/Service
Engine Soonlight should turn off. (A driving cycle
consists of a cold engine startup followed by mixed
city/highway driving.) No additional vehicle service is
required.
If theCheck Engine/Service Engine Soonlight
remains on, have your vehicle serviced at the first
available opportunity.
Readiness for Inspection/Maintenance (I/M)
testing
In some localities, it may be a legal requirement to
pass an I/M test of the on-board diagnostics system.
If your“Check Engine/Service Engine Soon”light is
on, refer to the description in theWarning lights
and chimessection of theInstrument cluster
chapter. Your vehicle may not pass the I/M test with
the“Check Engine/Service Engine Soon”light on.
2004 Mustang(mus)
Owners Guide (post-2002-fmt)
USA English(fus)
Maintenance and Specifications
193
Page 194 of 240

If the vehicle’s powertrain system or its battery has
just been serviced, the on-board diagnostics system
is reset to a“not ready for I/M test”condition. To
ready the on-board diagnostics system for I/M
testing, a minimum of 30 minutes of city and
highway driving is necessary as described below:
•First, at least 10 minutes of driving on an
expressway or highway.
•Next, at least 20 minutes driving in stop-and-go,
city-type traffic with at least four idle periods.
Allow the vehicle to sit for at least eight hours
without starting the engine. Then, start the engine
and complete the above driving cycle. The engine
must warm up to its normal operating temperature.
Once started, do not turn off the engine until the
above driving cycle is complete.
CHECKING AND ADDING POWER STEERING
FLUID
Check the power steering fluid. Refer to the
scheduled maintenance guide for the service interval
schedules. If adding fluid is necessary, use only
MERCONAT F.
If your vehicle is
equipped with the
OHV V6 engine,
check the power
steering fluid level with
the engine at normal
operating temperature.
1. Start the engine and
let it run until it
reaches normal
operating temperature
(the engine coolant
temperature gauge
indicator will be near
the center of the
normal area between H
and C).
FILL
HOT
2004 Mustang(mus)
Owners Guide (post-2002-fmt)
USA English(fus)
Maintenance and Specifications
194
Page 195 of 240

2. While the engine idles, turn the steering wheel
left and right several times.
3. Turn the engine off.
4. Check the fluid level on the dipstick. It should be
within the FULL HOT range. Do not add fluid if the
level is within this range.
5. If the fluid is low, add fluid in small amounts,
continuously checking the level until it reaches the
correct operating range. Be sure to put the cap back
on the reservoir.
If your vehicle is
equipped with a 4.6L
V8 engine,check the
power steering fluid
level with the engine at
ambient temperature.
Allow at least one-half
hour after driving for
the power steering
fluid to cool.
1. Start the engine and
allow the engine to
idle.
2. Turn the steering
wheel left and right
several times.
3. Turn the engine off.
4. Check the fluid level in the reservoir. It should be
between the MIN and MAX lines. Do not add fluid if
the level is within this range.
5. If the fluid is low, add fluid in small amounts,
continuously checking the level until it reaches the
correct operating range. Be sure to put the cap back
on the reservoir.
MAXMIN
2004 Mustang(mus)
Owners Guide (post-2002-fmt)
USA English(fus)
Maintenance and Specifications
195
Page 196 of 240

BRAKE FLUID RESERVOIR
The fluid level will drop
slowly as the brakes
wear, and will rise
when the brake
components are
replaced. Fluid levels below the“MAX”line that do
not trigger the brake system warning lamp are
within the normal operating range, there is no need
to add fluid. If the fluid levels are outside of the
normal operating range, the performance of your
brake system could be compromised, seek service
from your dealer immediately.
CLUTCH ADJUSTMENT (IF EQUIPPED)
Check the clutch
adjustment. Refer to
the scheduled
maintenance guide for
the service interval
schedules.
The clutch on your
vehicle is operated by a
cable. As necessary, adjust the clutch as described
below.
1. Turn the engine off and shift into 1 (First).
2. Put your foot under the clutch pedal and gently
pull it up until the pedal stops.
3. Push the clutch pedal down slowly. You will hear a
click as the clutch adjusts itself.
TRANSMISSION FLUID
Checking automatic transmission fluid
(if equipped)
Refer to your scheduled maintenance guide for
scheduled intervals for fluid checks and changes.
Your transmission does not consume fluid. However,
the fluid level should be checked if the transmission
is not working properly, i.e., if the transmission slips
or shifts slowly or if you notice some sign of fluid
leakage.
M
A
X
2004 Mustang(mus)
Owners Guide (post-2002-fmt)
USA English(fus)
Maintenance and Specifications
196
Page 197 of 240
![FORD MUSTANG 2004 4.G Owners Manual Automatic transmission fluid expands when warmed.
To obtain an accurate fluid check, drive the vehicle
until it is at normal operating temperature
(approximately 30 km [20 miles]). If your vehicle has FORD MUSTANG 2004 4.G Owners Manual Automatic transmission fluid expands when warmed.
To obtain an accurate fluid check, drive the vehicle
until it is at normal operating temperature
(approximately 30 km [20 miles]). If your vehicle has](/manual-img/11/5213/w960_5213-196.png)
Automatic transmission fluid expands when warmed.
To obtain an accurate fluid check, drive the vehicle
until it is at normal operating temperature
(approximately 30 km [20 miles]). If your vehicle has
been operated for an extended period at high
speeds, in city traffic during hot weather or pulling a
trailer, the vehicle should be turned off for about 30
minutes to allow fluid to cool before checking.
1. Drive the vehicle 30 km (20 miles) or until it
reaches normal operating temperature.
2. Park the vehicle on a level surface and engage the
parking brake.
3. With the parking brake engaged and your foot on
the brake pedal, start the engine and move the
gearshift lever through all of the gear ranges. Allow
sufficient time for each gear to engage.
4. Latch the gearshift lever in P (Park) and leave the
engine running.
5. Remove the dipstick, wiping it clean with a clean,
dry lint free rag. If necessary, refer toIdentifying
components in the engine compartmentin this
chapter for the location of the dipstick.
6. Install the dipstick making sure it is fully seated in
the filler tube.
7. Remove the dipstick and inspect the fluid level.
The fluid should be in the designated area for
normal operating temperature or ambient
temperature.
Low fluid level
Do not drive the
vehicle if the fluid level
is at the bottom of the
dipstick and the ambient temperature is above 10°C
(50°F).
Correct fluid level
The transmission fluid should be checked at normal
operating temperature 66°C-77°C (150°F-170°F) on
a level surface. The normal operating temperature
can be reached after approximately 30 km (20 miles)
of
driving.
2004 Mustang(mus)
Owners Guide (post-2002-fmt)
USA English(fus)
Maintenance and Specifications
197
Page 198 of 240

You can check the fluid without driving if the
ambient temperature is above 10°C (50°F). However,
if fluid is added at this time, an overfill condition
could result when the vehicle reaches normal
operating temperature.
The transmission fluid
should be in this range
if at normal operating
temperature (66°C-77°C [150°F-170°F]).
The transmission fluid
should be in this range
if at ambient
temperature (10°C-35°C [50°F-95°F]).
High fluid level
Fluid levels above the
safe range may result
in transmission failure.
An overfill condition of transmission fluid may cause
shift and/or engagement concerns and/or possible
damage.
High fluid levels can be caused by an overheating
condition.
Adjusting automatic transmission fluid levels
Before adding any fluid, make sure the correct type
is used. The type of fluid used is normally indicated
on the dipstick and also in theLubricant
specificationssection in this chapter.
Use of a non-approved automatic transmission
fluid may cause internal transmission
component damage.
If necessary, add fluid in 250 ml (1/2 pint)
increments through the filler tube until the level is
correct.
If an overfill occurs,
excess fluid should be
removed by a qualified
technician.
2004 Mustang(mus)
Owners Guide (post-2002-fmt)
USA English(fus)
Maintenance and Specifications
198
Page 199 of 240
An overfill condition of transmission fluid may
cause shift and/or engagement concerns and/or
possible damage.
Do not use supplemental transmission fluid
additives, treatments or cleaning agents. The use of
these materials may affect transmission operation
and result in damage to internal transmission
components.
Checking and adding manual transmission fluid
(if equipped)
1. Clean the filler plug.
2. Remove the filler
plug and inspect the
fluid level.
3. Note: There are two different manual
transmissions used in this vehicle and they have
different fluid levels. For vehicles equipped with a
V6 engine and Cobra the correct manual
transmission fill level is at the lower edge of the
filler hole. For vehicles equipped with a V8 engine
(except Cobra) the correct manual transmission fill
level is 1.3 cm (1/2 inch) below the edge of the filler
hole.
•Fill level for V6 and
Cobra
2004 Mustang(mus)
Owners Guide (post-2002-fmt)
USA English(fus)
Maintenance and Specifications
199
Page 200 of 240

•Fill level for V8
(except Cobra)
4. Add enough fluid through the filler opening to
bring the fluid up to the recommended levels.
5. Install and tighten the fill plug securely.
Use only fluid that meets Ford specifications. Refer
toLubricant Specificationsin this chapter.
INFORMATION ABOUT UNIFORM TIRE QUALITY
GRADING
New vehicles are fitted
with tires that have a
rating on them called
Tire Quality Grades.
The Quality grades can
be found where
applicable on the tire sidewall between tread
shoulder and maximum section width. For example:
•Treadwear 200 Traction AA Temperature A
These Tire Quality Grades are determined by
standards that the United States Department of
Transportation has set.
Tire Quality Grades apply to new pneumatic tires for
use on passenger cars. They do not apply to deep
tread, winter-type snow tires, space-saver or
temporary use spare tires, tires with nominal rim
diameters of 10 to 12 inches or limited production
tires as defined in Title 49 Code of Federal
Regulations Part 575.104(c)(2).
U.S. Department of Transportation-Tire quality
grades:The U.S. Department of Transportation
requires Ford to give you the following information
about tire grades exactly as the government has
written it.
2004 Mustang(mus)
Owners Guide (post-2002-fmt)
USA English(fus)
Maintenance and Specifications
200