Page 749 of 865

ONBOARD DIAGNOSTIC SYSTEM (OBD II)
Your vehicle is equipped with a sophisticated onboard
diagnostic system called OBD II. This system monitors
the performance of the emissions, engine, and automatic
transmission control systems. When these systems are
operating properly, your vehicle will provide excellent
performance and fuel economy, as well as engine emis-
sions well within current government regulations.
If any of these systems require service, the OBD II system
will turn on the “Malfunction Indicator Light (MIL).” It
will also store diagnostic codes and other information to
assist your service technician in making repairs. Al-
though your vehicle will usually be drivable and not
need towing, see your authorized dealer for service as
soon as possible.
CAUTION!
•Prolonged driving with the MIL on could cause
further damage to the emission control system. It
could also affect fuel economy and driveability.
The vehicle must be serviced before any emissions
tests can be performed.
• If the MIL is flashing, while the engine is running,
severe catalytic converter damage and power loss
will soon occur. Immediate service is required.
Loose Fuel Filler Cap Message
If the vehicle diagnostic system determines
that the fuel filler cap is loose, improperly
installed, or damaged, a loose gascap indicator
will display in the EVIC/DID telltale display
area. Refer to “Electronic Vehicle Information Center
(EVIC)” or “Driver Information Display (DID)” in “Un-
derstanding Your Instrument Panel” for further informa-
tion. Tighten the fuel filler cap properly and press the
7
MAINTAINING YOUR VEHICLE 747
Page 786 of 865

CAUTION!
If a transmission fluid leak occurs, visit your autho-
rized dealer immediately. Severe transmission dam-
age may occur. Your authorized dealer has the proper
tools to adjust the fluid level accurately.
Fluid Level Check — Six-Speed Transmission
It is best to check the fluid level when the transmission is
at normal operating temperature (170-180°F / 77-82°C).
This normally occurs after at least 15 miles (25 km) of
driving. At normal operating temperature the fluid can-
not be held comfortably between the fingertips. You can
read the transmission sump temperature in the EVIC/
DID screen (refer to “Electronic Vehicle Information
Center [EVIC]” or “Driver Information Display (DID)”
for further information).Use the following procedure to check the transmission
fluid level properly:
1. Monitor the transmission temperature using the
EVIC/DID screen, and operate the vehicle as required
to reach the normal operating temperature. If the
transmission is not functioning properly, or the vehicle
cannot be driven, see the NOTE and CAUTION below
about checking the fluid level at colder temperatures.
2. Park the vehicle on level ground.
3. Run the engine at normal idle speed for at least 60 seconds, and leave the engine running for the rest of
this procedure.
4. Fully apply the parking brake, and press the brake pedal.
5.
Place the shift lever momentarily into each gear position
(allowing time for the transmission to fully engage in
each position), ending with the transmission in PARK.
784 MAINTAINING YOUR VEHICLE
Page 826 of 865

MAINTENANCE SCHEDULE
Your vehicle is equipped with an automatic oil change
indicator system. The oil change indicator system will
remind you that it is time to take your vehicle in for
scheduled maintenance.
Based on engine operation conditions, the oil change
indicator message will illuminate. This means that ser-
vice is required for your vehicle. Operating conditions
such as frequent short-trips, trailer tow, extremely hot or
cold ambient temperatures, and E85 fuel usage will
influence when the “Oil Change Required” message is
displayed. Severe Operating Conditions can cause the
change oil message to illuminate as early as 3,500 miles
(5,600 km) since last reset. Have your vehicle serviced as
soon as possible, within the next 500 miles (805 km).
Your authorized dealer will reset the oil change indicator
message after completing the scheduled oil change. If a
scheduled oil change is performed by someone other
than your authorized dealer, the message can be reset byreferring to the steps described under “Electronic Vehicle
Information Center (EVIC)” or “Driver Information Dis-
play (DID)” in “Understanding Your Instrument Panel”
for further information.
NOTE: 1500 Models Only
•
Under no circumstances should oil change intervals
exceed 10,000 miles (16,000 km) or twelve months on
1500 trucks, whichever comes first.
2500 – 3500 Models
• Under no circumstances should oil change intervals
exceed 8,000 miles (13,000 km) or twelve months on
2500 – 3500 trucks, whichever comes first.
Severe Duty All Models
•
Change Engine Oil at 4000 miles (6,500 km) if the vehicle
is operated in a dusty and off road environment. This
type of vehicle use is considered Severe Duty.
824 MAINTENANCE SCHEDULES