Hummer H3. Manual — part 485

The fourth through ninth digits are the last 6 digits of the VIN.

DIAGNOSTIC INFORMATION AND PROCEDURES

DIAGNOSTIC STARTING POINT - ENGINE MECHANICAL

Begin the system diagnosis by reviewing the Disassembled Views, Engine Component
Description, and Lubrication Description. Reviewing the description and operation
information helps you determine the correct symptom diagnostic procedure when a malfunction
exists. Reviewing the description and operation information also helps you determine if the
condition described by the customer is normal operation. Refer to Symptoms - Engine
Mechanical in order to identify the correct procedure for diagnosing the system and where the
procedure is located.

SYMPTOMS - ENGINE MECHANICAL

Strategy Based Diagnostics

1. Perform the Diagnostic System Check - Vehicle before using the symptom tables.

2. Review the system operations in order to familiarize yourself with the system functions.

Refer to Disassembled Views, Engine Component Description, and Lubrication
Description.

All diagnosis on a vehicle should follow a logical process. Strategy based diagnostics is a uniform
approach for repairing all systems. The diagnostic flow may always be used in order to resolve a
system condition. The diagnostic flow is the place to start when repairs are necessary. For a
detailed explanation, refer to Strategy Based Diagnosis .

Visual/Physical Inspection

Inspect for aftermarket devices which could affect the operation of the engine. Refer to
Checking Aftermarket Accessories .

Inspect the easily accessible or visible system components for obvious damage or conditions
which could cause the symptom.

Inspect for the correct oil level, proper oil viscosity, and correct filter application.

Verify the exact operating conditions under which the concern exists. Note factors such as
engine RPM, ambient temperature, engine temperature, amount of engine warm-up time,
and other specifics.

Compare the engine sounds, if applicable, to a known good engine and make sure you are
not trying to correct a normal condition.

2008 Hummer H3

2008 ENGINE Engine Mechanical - 5.3L - H3

Intermittent

Test the vehicle under the same conditions that the customer reported in order to verify the system
is operating properly.

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the
symptom:

Base Engine Misfire without Internal Engine Noises

Base Engine Misfire with Abnormal Internal Lower Engine Noises

Base Engine Misfire with Abnormal Valve Train Noise

Base Engine Misfire with Coolant Consumption

Base Engine Misfire with Excessive Oil Consumption

Engine Noise on Start-Up, but Only Lasting a Few Seconds

Upper Engine Noise, Regardless of Engine Speed

Lower Engine Noise, Regardless of Engine Speed

Engine Noise Under Load

Engine Will Not Crank - Crankshaft Will Not Rotate

Coolant in Combustion Chamber

Coolant in Engine Oil

Engine Compression Test

Cylinder Leakage Test

Oil Consumption Diagnosis

Oil Pressure Diagnosis and Testing

Oil Leak Diagnosis

Crankcase Ventilation System Inspection/Diagnosis

Drive Belt Chirping, Squeal, and Whine Diagnosis

Drive Belt Rumbling and Vibration Diagnosis

Drive Belt Falls Off and Excessive Wear Diagnosis

Drive Belt Tensioner Diagnosis

BASE ENGINE MISFIRE WITHOUT INTERNAL ENGINE NOISES

2008 Hummer H3

2008 ENGINE Engine Mechanical - 5.3L - H3

Cause

Correction

Fuel injector harness connectors are
connected to the incorrect fuel
injectors/cylinders

Relocate the fuel injector harness connectors,
as necessary.

Abnormalities, such as severe cracking,
bumps, or missing areas in the accessory drive
belt
Abnormalities in the accessory drive system
and/or components may cause engine RPM
variations and lead to a misfire diagnostic
trouble code (DTC). A misfire code may be
present without an actual misfire condition.

Replace the drive belt. Refer to Drive Belt
Replacement - Accessory.

Worn, damaged, or mis-aligned accessory
drive components or excessive pulley runout
May lead to a misfire DTC.
A misfire code may be present without an
actual misfire condition.

Inspect the components and repair or replace,
as required.

Loose or improperly installed engine flex
plate or crankshaft balancer
A misfire code may be present without an
actual misfire condition.

Repair or replace the flex plate and/or
balancer, as required. Refer to Automatic
Transmission Flex Plate Replacement, or
Crankshaft Balancer Replacement.

Restricted exhaust system
A severe restriction in the exhaust flow can
cause significant loss of engine performance
and may set a DTC. Possible causes of
restrictions include collapsed or dented pipes
or plugged mufflers and/or catalytic
converters.

Repair or replace, as required.

Improperly installed or damaged vacuum
hoses

Repair or replace, as required.

Improper sealing between the intake manifold
and cylinder heads or throttle body

Replace the intake manifold, gaskets,
cylinder heads, and/or throttle body, as
required.

Improperly installed or damaged manifold
absolute pressure (MAP) sensor
The sealing grommet of the MAP sensor
should not be torn or damaged.

Repair or replace the MAP sensor, as
required.

Worn or loose rocker arms

Replace the valve rocker arms, as required.

2008 Hummer H3

2008 ENGINE Engine Mechanical - 5.3L - H3

The rocker arm bearing end caps and/or
needle bearings should be intact and in the
proper position.
Worn or bent pushrods

Replace the pushrods.

Inspect the top of the pistons for valve
contact. If the top of the piston shows
valve contact, replace the piston and pin
assembly.

Stuck valves
Carbon buildup on the valve stem can cause
the valve to not close properly.

Repair or replace, as required.

Excessively worn or mis-aligned timing chain Replace the timing chain and sprockets, as

required.

Worn camshaft lobes

Replace the camshaft and valve lifters.

Excessive oil pressure
A lubrication system with excessive oil
pressure may lead to excessive valve lifter
pump-up and loss of compression.

1. Perform an oil pressure test. Refer to

Oil Pressure Diagnosis and Testing.

2. Repair or replace the oil pump, as

required.

Faulty cylinder head gaskets and/or cracking
or other damage to the cylinder heads and
engine block cooling system passages
Coolant consumption may or may not cause
the engine to overheat.

1. Inspect for spark plugs saturated by

coolant. Refer to Spark Plug
Inspection .

2. Inspect the cylinder heads, engine

block, and/or head gaskets. Refer to
Coolant in Combustion Chamber.

3. Repair or replace, as required.

Worn piston rings
Oil consumption may or may not cause the
engine to misfire.

1. Inspect the spark plugs for oil deposits.

Refer to Spark Plug Inspection .

2. Inspect the cylinders for a loss of

compression. Refer to Engine
Compression Test.

3. Perform cylinder leak down and

compression testing to identify the
cause. Refer to Cylinder Leakage
Test.

4. Repair or replace, as required.

A damaged crankshaft reluctor wheel

Replace the sensor and/or crankshaft, as

2008 Hummer H3

2008 ENGINE Engine Mechanical - 5.3L - H3