Hummer H2. Manual — part 1695

Fig. 18: Engine Identification Location
Courtesy of GENERAL MOTORS CORP.

The vehicle identification number (VIN) is located on the left side rear of the engine block (1) and is typically a
nine digit number stamped or laser-etched onto the engine at the vehicle assembly plant.

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The first digit identifies the division.

2004 Hummer H2

2004 ENGINE Engine Mechanical - 4.8L, 5.3L, and 6.0L - Hummer H2

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The second digit identifies the model year.

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The third digit identifies the assembly plant.

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The fourth through ninth digits are the last six 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 ,
Lubrication Description , New Product Information , and Drive Belt System Description . Reviewing the
description and operation information will help you determine the correct symptom diagnostic procedure when
a malfunction exists. Reviewing the description and operation information will also help 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 - Engine Controls in Engine Controls - 6.0L before using the

symptom tables, if applicable.

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

Disassembled Views , Engine Component Description , Lubrication Description , New Product
Information , and Drive Belt System 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 in General Information.

Visual/Physical Inspection

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Inspect for aftermarket devices which could affect the operation of the Engine. Refer to Checking
Aftermarket Accessories in Wiring Systems.

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

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

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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.

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

Intermittent

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

2004 Hummer H2

2004 ENGINE Engine Mechanical - 4.8L, 5.3L, and 6.0L - Hummer H2

properly.

Symptom List

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

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Base Engine Misfire without Internal Engine Noises

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Base Engine Misfire with Abnormal Internal Lower Engine Noises

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Base Engine Misfire with Abnormal Valve Train Noise

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Base Engine Misfire with Coolant Consumption

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Base Engine Misfire with Excessive Oil Consumption

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Engine Compression Test

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

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Upper Engine Noise, Regardless of Engine Speed

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Lower Engine Noise, Regardless of Engine Speed

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Engine Noise Under Load

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Engine Will Not Crank - Crankshaft Will Not Rotate

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Coolant in Combustion Chamber

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Coolant in Engine Oil

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Oil Consumption Diagnosis

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Oil Pressure Diagnosis and Testing

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Oil Leak Diagnosis

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Cylinder Leakage Test

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Drive Belt Chirping Diagnosis

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Drive Belt Squeal Diagnosis

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Drive Belt Whine Diagnosis

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Drive Belt Rumbling Diagnosis

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Drive Belt Vibration Diagnosis

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Drive Belt Falls Off Diagnosis

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Drive Belt Excessive Wear Diagnosis

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Drive Belt Tensioner Diagnosis

BASE ENGINE MISFIRE WITHOUT INTERNAL ENGINE NOISES

Base Engine Misfire without Internal Engine Noises

Cause

Correction

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

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

2004 Hummer H2

2004 ENGINE Engine Mechanical - 4.8L, 5.3L, and 6.0L - Hummer H2

misfire DTC. A misfire code may be present without an
actual misfire condition.
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 flywheel or crankshaft
balancer
A misfire code may be present without an actual misfire
condition.

Repair or replace the flywheel and/or
balancer as required. Refer to Engine
Flywheel 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 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
The rocker arm bearing end caps and/or needle bearings
should be intact and in the proper position.

Replace the valve rocker arms as required.

Worn or bent pushrods

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Replace the pushrods.

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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 not to
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.

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Perform an oil pressure test. Refer to
Oil Pressure Diagnosis and
Testing .

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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 - Refer to Diagnostic Starting Point -

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Inspect for spark plugs saturated by
coolant. Refer to Spark Plug
Inspection in Engine Controls -

2004 Hummer H2

2004 ENGINE Engine Mechanical - 4.8L, 5.3L, and 6.0L - Hummer H2