check engine CHEVROLET C/K 2003 Service Manual

6-42
Checking Brake Fluid (Hydro Max System)
Apply the brake pedal several times with the ignition
off. Then clean one of the reservoir caps and the area
around the cap, and remove it. The fluid level should be
even with the bottom ring of the filler opening.
The Hydro Max
brake fluid reservoir
is located in the
engine compartment
on the driver's side
of the vehicle.
If it's low, add enough fluid to fill the reservoir to the
proper level.Checking Brake Fluid (Hydro Boost System)
Apply the brake pedal several times with the ignition
off. Clean the cover and the side of the reservoir.
Check to see if the fluid level inside the reservoir falls
within the MIN/MAX level indicator on the side of
the reservoir.
The Hydro Boost
brake fluid reservoir
is located in the
engine compartment
on the driver's side
of the vehicle.
If it's low, add enough fluid to fill the reservoir to the
proper level.

6-55 Primary Fuel Filter and Water Separator
(If Equipped)
If you have a diesel engine,
you may have this spin
-on
filter. It is located on the
driver's side frame rail.
It has a clear plastic drain bowl at the bottom. Check the
drain bowl occasionally for any water or particles.
To drain the bowl, do the following:
1. Shut off the engine.
2. Partially open the drain valve at the bottom of
the filter.
See ªEngine Oilº in the Index for proper disposal
procedures.
Secondary Fuel Filter and Water
Separator/Heater (If Equipped)
If you have a Caterpillar

diesel engine, you may also
have this spin
-on filter and
fuel separator/heater. It will
be mounted in the engine
compartment on the driver's
side of the vehicle.
It has a metal drain bowl at the bottom. Occasionally,
check the bowl for any water or particles.
To check or drain the bowl, do the following:

Shut off the engine.

Push up on the spring loaded drain valve until clear
fuel is flowing from the valve.
The particles or water will drain out first. See ªEngine
Oilº in the Index for proper disposal procedures.

6-56 Automatic Ether Injection System
(If Equipped)
If you have a Caterpillar
diesel engine, you may have
this feature. The ether
cylinder is located in the
engine compartment on the
driver's side of the vehicle.To change an empty ether cylinder, follow these steps.
1. Loosen the screw head on the cylinder
-to-bracket
clamp.
2. Spread the clamp apart.
3. Clean any dirt from the neck of the cylinder and the
top of the valve before you take out the cylinder.
4. Check the inside of the valve for any foreign matter.
Clean the valve as necessary.
5. Cover the valve to protect it from dirt and take out
the cylinder.
6. Install a new gasket whenever you take out the
cylinder. Use only one gasket and spread a light film
of clean oil on it before installation.
7. Put in the new cylinder. Turn it clockwise until it just
starts to contact the gasket.
8. Tighten the cylinder another half turn (180 degrees).
Don't over
-tighten.
9. Retighten the cylinder clamp.

6-78 Headlamp Wiring
The headlamp wiring is protected by a circuit breaker in
the light switch. An electrical overload will cause the
lights to go on and off, or in some cases to remain off.
If this happens, have your headlamp wiring checked
right away.
Windshield Wiper Fuses
The windshield wiper motor is protected by a circuit
breaker inside the motor and a circuit breaker or fuse in
the fuse block. If the motor overheats, the wipers will
stop until the motor cools. If the overload is caused by
an electrical problem, be sure to get it fixed.
Fusible Links
A fusible link is a short piece of wire several gauge sizes
smaller than the circuit it protects. It will melt in an
overload situation, opening the circuit.
Your starter and other circuits have these fusible links.
The size is printed on the insulation. If the insulation is
burned beyond recognition, consult your GM dealer for
the proper size. Replace a fusible link with one of the
same size and insulation type. Fusible link insulation is a
special purpose high
-temperature material.
The hydraulic brake booster motor feed circuit and
starter circuit are protected by a fusible link. Vehicles
with a diesel engine have a fusible link for the intake
heater feed circuit.

6-88 Engine Oil with Filter Capacity
Engine Quarts (Liters)
7.2L** 30.0 (28.4)*
8.1L** 6.5 (6.1)
7.8L** 23.8 (22.5 )
6.6L** 14.6 (13.8)
*Additional oil is required with auxiliary oil filter
systems. Make sure to add enough extra oil to fill the
auxiliary oil filter system. For vehicles equipped with
the LUBERFINER 750
-C, add 14 quarts (13.25 L).
** Check fill level on the oil indicator after initial fill to
make sure it is actually full. Oil level may vary
depending on vehicle option content.
Fuel Tank Capacity
C4/C5 Models Gallons (Liters). . . . . . . . . . . . . . . . .
Standard* 41 (155.2). . . . . . . . . . . . . . . . . . . . . . . .
Optional 40 (151.4). . . . . . . . . . . . . . . . . . . . . . . . . .
Optional 60 (227.1). . . . . . . . . . . . . . . . . . . . . . . . . .
Optional 80 (302.8). . . . . . . . . . . . . . . . . . . . . . . . . .
C6/C7/C8 Models Gallons (Liters). . . . . . . . . . . . . .
Standard 50 (189.2). . . . . . . . . . . . . . . . . . . . . . . . .
Optional 35 (132.4). . . . . . . . . . . . . . . . . . . . . . . . . .
Optional 50 (189.2). . . . . . . . . . . . . . . . . . . . . . . . . .
Optional
70 (264.8) . . . . . . . . . . . . . . . . . . . . . . . .
Optional75 (283.8) . . . . . . . . . . . . . . . . . . . . . . . .
Optional& 100 (378.5). . . . . . . . . . . . . . . . . . . . . . .
* One 25
-gallon (94.6 L) tank and one 16-gallon
(60.6 L) tank

Two 35
-gallon (132.4 L) tanks
One 25
-gallon (94.6 L) tank and One 50-gallon
(189.2 L) tank
&Two 50
-gallon (189.2 L) tanks

7-4
Part A: Scheduled Maintenance
Services
Using Your Maintenance Schedule
We at General Motors want to help you keep your
vehicle in good working condition. But we don't know
exactly how you'll drive it. You may drive very short
distances only a few times a week. Or you may drive
long distances all the time in very hot, dusty weather.
You may use your vehicle in making deliveries or in
many other ways.
Because of all the different ways people use their
vehicles, maintenance needs vary. You may need more
frequent checks and replacements. So please read the
following and note how you drive. If you have any
questions on how to keep your vehicle in good
condition, see your dealer.
This part tells you the maintenance services you should
have done and when you should schedule them. If you
go to your dealer for your service needs, you'll know
that GM
-trained and supported service people will
perform the work using genuine GM parts.The proper fluids and lubricants to use are listed in
Part C. Make sure whoever services your vehicle uses
these. All parts should be replaced and all necessary
repairs done before you or anyone else drives
the vehicle.
This schedule is for vehicles that:

carry passengers and cargo within recommended
limits. You will find these limits on your vehicle's
GVW Rating label. See ªLoading Your Vehicleº in
the Index.

are driven on reasonable road surfaces within legal
driving limits.

use the recommended fuel. See ªFuelº in the Index.
Scheduled Maintenance Supplements
If your vehicle has a Caterpillar diesel engine, your
owner's manual is supplemented by the Caterpillar
Diesel Engine Operation & Maintenance Manual. If
your vehicle has an Allison transmission, your owner's
manual is supplemented by an Allison Transmission
Operator's Manual. Always refer to these manuals for
related maintenance services.

7-5
Scheduled Maintenance
The services shown in this schedule up to 100,000 miles
(166 000 km) should be repeated after 100,000 miles
(166 000 km) at the same intervals for the life of
this vehicle. The services shown after 100,000 miles
(166 000 km) should be repeated at the same miles (km)
after those intervals for the life of this vehicle.
Gasoline engine vehicles have a computer that lets you
know when to change your engine oil. This is not based
on mileage, but on engine revolutions and engine
operating temperature. When the computer has
calculated that the oil needs changing, the GM Oil Life
System will indicate that a change is necessary.
The ªFootnotesº at the end of this Maintenance
Schedule further explain maintenance services.
See ªScheduled Maintenance Supplementsº earlier in
this section.
100 Miles (160 km)

Wheel stud nut service. (46)
1,000 Miles (1 600 km)

Wheel stud nut service. (46)

Rear axle air shift motor service.(11)

L18/LB7 Engines Only: Clutch pedal free
travel service. (10)
7,500 Miles (12 000 km)

Gasoline Engine Only: Check Oil Life System.
If engine oil and filter are changed, reset system.
See ªEngine Oilº in the Index. (3)(9)

Check fluid levels (or every 3 months, whichever
occurs first). (1)(6)

Chassis lubrication service (or every 6 months,
whichever occurs first). (12)

Wheels and tires service. (15)

Parking brake service (or every 6 months, whichever
occurs first). (8)

L18/LB7 Engines Only: Clutch pedal free
travel service. (10)
10,000 Miles (16 000 km)

DURAMAX Diesel Only: Change engine oil
and filter (or every 12 months, whichever
occurs first). (2)(3)

7-6
15,000 Miles (24 000 km)

Gasoline Engine Only: Check Oil Life System.
If engine oil and filter are changed, reset system.
See ªEngine Oilº in the Index. (3)(9)

Chassis lubrication service (or every 6 months,
whichever occurs first). (12)

Check fluid levels (or every 3 months, whichever
occurs first). (1)(6)

DURAMAX Diesel Only: Replace fuel filter.

Steering system service. (13)

Front and rear suspension service. (14)

Spring
-to-axle U-bolts and shackle bolts
service. (16)

Exhaust system service (or every 6 months,
whichever occurs first). (3)(4)(17)

Wheels and tires service. (15)

Hydraulic brake service (or every 6 months,
whichever occurs first). (7)(46)

Parking brake service (or every 6 months, whichever
occurs first). (8)

Thermostatically controlled engine cooling fan
service. (4)(20)

Shields and underhood insulation service. (4)(5)(21)

L18/LB7 Engines Only: Clutch pedal free
travel service. (10)
20,000 Miles (32 000 km)

DURAMAX Diesel Only: Change engine oil
and filter (or every 12 months, whichever occurs
first). (2)(3)

Air compressor dry element pleated paper air strainer
service (or every 2 months or every 800 hours,
whichever occurs first).
22,500 Miles (36 000 km)

Gasoline Engine Only: Check Oil Life System.
If engine oil and filter are changed, reset system.
See ªEngine Oilº in the Index. (3)(9)

Check fluid levels (or every 3 months, whichever
occurs first). (1)(6)

Chassis lubrication service (or every 6 months,
whichever occurs first). (12)

Inspect door hinge pins and bushings and replace
as necessary.

Cooling system service. Clean the cooling system
filler cap with clean water, clean the core, pressure
test the cap and the system for proper pressure
capability and inspect condition of cooling and
heater hoses and clamps. Replace hoses if cracked,
swollen or damaged.

7-7
Wheel bearing (grease type) service (or every
24 months, whichever occurs first, and whenever
hubs are removed). (23)(46)
Wheels and tires service. (15)
Parking brake service (or every 6 months, whichever
occurs first). (8)
Air intake system service (or every 24 months,
whichever occurs first). (4)(5)(24)
Evaporative Control System service (if equipped) (or
every 24 months, whichever occurs first). (3)(26)

Rear axle air shift motor service. (11)
Air brake service (or every 6 months, whichever
occurs first). (39)
Air brake automatic slack adjuster service
(or every 500 hours, whichever occurs first). (40)
Check air brake relay valve operation and check
for leaks (or every month, or every 300 hours,
whichever occurs first).
Clean air brake application valve (or every 3 months,
or every 300 hours, whichever occurs first); lubricate
linkage.
Air brake chamber service (or every 2 months,
whichever occurs first). (41)Trailer brake hand control valve service (or every
3 months, or every 900 hours, whichever
occurs first). (42)
L18/LB7 Engines Only: Clutch pedal free
travel service. (10)
30,000 Miles (48 000 km)
Gasoline Engine Only: Check Oil Life System.
If engine oil and filter are changed, reset system.
See ªEngine Oilº in the Index. (3)(9)
DURAMAX Diesel Only: Change engine oil
and filter (or every 12 months, whichever occurs
first). (2)(3)
Check fluid levels (or every 3 months, whichever
occurs first). (1)(6)
DURAMAX Diesel Only: Replace fuel filter.
Chassis lubrication service (or every 6 months,
whichever occurs first). (12)
Replace fuel filter(s) (or every 12 months, whichever
occurs first). (3)
Steering system service. (13)
Front and rear suspension service. (14)
Spring
-to-axle U-bolts and shackle bolts
service. (16)
Exhaust system service (or every 6 months,
whichever occurs first). (3)(4)(17)
(Continued)

7-8
30,000 Miles (48 000 km) (Continued)

Wheels and tires service. (15)

Hydraulic brake service (or every 6 months,
whichever occurs first). (7)(46)

Parking brake service (or every 6 months, whichever
occurs first). (8)

C600, C700 and C800 Gasoline Engines Only:
Engine drive belts service (or every 12 months,
whichever occurs first). (18)

Thermostatically controlled engine cooling fan
service. (4)(20)

Shields and underhood insulation service. (4)(5)(21)

L18/LB7 Engines Only: Clutch pedal free
travel service. (10)
37,500 Miles (60 000 km)

Gasoline Engine Only: Check Oil Life System.
If engine oil and filter are changed, reset system.
See ªEngine Oilº in the Index. (3)(9)

Check fluid levels (or every 3 months, whichever
occurs first). (1)(6)

Chassis lubrication service (or every 6 months,
whichever occurs first). (12)

Wheels and tires service. (15)

Parking brake service (or every 6 months, whichever
occurs first). (8)
L18/LB7 Engines Only: Clutch pedal free
travel service. (10)
40,000 Miles (64 000 km)

DURAMAX Diesel Only: Change engine oil
and filter (or every 12 months, whichever occurs
first). (2)(3)

Air compressor dry element pleated paper air strainer
service (or every 2 months or every 800 hours,
whichever occurs first).
45,000 Miles (72 000 km)

Gasoline Engine Only: Check Oil Life System.
If engine oil and filter are changed, reset system.
See ªEngine Oilº in the Index. (3)(9)

Check fluid levels (or every 3 months, whichever
occurs first). (1)(6)

DURAMAX Diesel Only: Replace fuel filter.

Chassis lubrication service (or every 6 months,
whichever occurs first). (12)

Cooling system service. Clean the cooling system
filler cap with clean water, clean the core, pressure
test the cap and the system for proper pressure
capability and inspect condition of cooling and
heater hoses and clamps. Replace hoses if cracked,
swollen or damaged.