Hummer H2. Manual — part 1489

Fuel System

z

Inspect both injector fuses for being open. An open injector fuse causes 4
ignition coils and 4 injectors not to operate. Replace the fuse. Inspect the
ignition coil circuits and the injector circuits for an intermittent short to ground.

z

Inspect for incorrect fuel pressure. Refer to Fuel System Diagnosis .

z

Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-
Fuel Diagnosis (without Special Tool and E85) or Alcohol/Contaminants-in-
Fuel Diagnosis (with Special Tool) .

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Inspect the fuel injectors. Refer to Fuel Injector Coil Test .

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Inspect for the following that may cause the engine to run rich:

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Water intrusion in the heated oxygen sensor (HO2S) connector

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Engine oil contaminated by fuel

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An evaporative emission (EVAP) canister purge condition

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Incorrect fuel pressure - Refer to Fuel System Diagnosis .

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Leaking fuel injectors - Refer to Fuel System Diagnosis .

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An inaccurate mass air flow (MAF) sensor

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Blockage on the inlet screen of the MAF sensor - Refer to Mass Air
Flow (MAF)/Intake Air Temperature (IAT) Sensor Replacement .

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Vacuum hoses that are split, kinked, or improperly connected

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An air intake duct that is collapsed or restricted - Refer to Air Cleaner
Resonator Outlet Duct Replacement .

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An air filter that is dirty or restricted - Refer to Air Cleaner Element
Replacement .

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Inspect for the following conditions that may cause the engine to run lean:

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Water intrusion in the HO2S connector

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An exhaust leak between the HO2S and the engine - Refer to Exhaust
Leakage in Engine Exhaust.

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Vacuum leaks

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Incorrect fuel pressure - Refer to Fuel System Diagnosis .

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Restricted fuel injectors - Refer to Fuel Injector Balance Test with
Special Tool or Fuel Injector Balance Test with Tech 2 .

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An inaccurate MAF sensor

NOTE:

Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and
Notices.

NOTE:

Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and
Notices.

2004 Hummer H2

2004 ENGINE PERFORMANCE Engine Controls (Troubleshooting) - 4.8L, 5.3L, and 6.0L - Hummer H2

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Fuel contamination - Refer to Alcohol/Contaminants-in-Fuel Diagnosis
(without Special Tool and E85) or Alcohol/Contaminants-in-Fuel
Diagnosis (with Special Tool) .

{

Vacuum hoses that are split, kinked, or improperly connected

Sensor/System

Use a scan tool in order to monitor the knock sensor (KS) system for excessive spark
retard activity. Refer to Knock Sensor (KS) System Description .

Ignition System

z

Verify that both fuel injector fuses are not open. An open fuel injector fuse
causes 4 ignition coils and 4 fuel injectors not to operate. Inspect the ignition
coil circuit and the injector circuits for an intermittent short to ground. Refer to
Circuit Testing in Wiring Systems. Replace the fuse.

z

Soak the secondary ignition system with water from a spray bottle. Soaking the
secondary ignition system may help locate damaged or deteriorated
components. Look and listen for arcing or misfiring as water is applied.

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Inspect for proper ignition voltage output with the J 26792 Spark Tester.

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Remove the spark plugs and inspect for the following:

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Correct heat range

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Wet plugs

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Cracks

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Wear

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Improper gap

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Burned electrodes

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Heavy deposits

Refer to Spark Plug Inspection .

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An improper spark plug gap will cause a driveability problem. Gap the spark
plugs using a wire gauge gap tool. Refer to Spark Plug Replacement .

z

Determine the cause of the fouling before replacing the spark plugs.

z

Monitor the Misfire Current Counters while driving the vehicle within the
conditions that the misfire occurred. If a misfiring cylinder can be located with
a misfire, use the DTC P0300 table for diagnosis. Refer to DTC P0300 .

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Inspect for loose ignition coil grounds. Refer to Electronic Ignition (EI)
System Diagnosis .

Engine
Mechanical

z

Verify that the engine coolant temperature (ECT) is not above 130°C (266°F).
This condition causes the PCM to operate in Engine Coolant Over Temperature-
Fuel Disabled Mode. While in Engine Coolant Over Temperature-Fuel Disabled
Mode, the PCM will disable the fuel injectors to 4 cylinders at a time to keep
engine temperatures from reaching damaging levels. The driver may perceive
the Engine Coolant Over Temperature-Fuel Disabled Mode as a lack of power,
miss, or rough idle. If the vehicle operates in Engine Coolant Over
Temperature-Fuel Disabled Mode, refer to Engine Overheating in Engine
Cooling for diagnosis.

2004 Hummer H2

2004 ENGINE PERFORMANCE Engine Controls (Troubleshooting) - 4.8L, 5.3L, and 6.0L - Hummer H2

DETONATION/SPARK KNOCK

Detonation/Spark Knock

z

Inspect for excessive oil in the combustion chambers and leaking valve seals.
Refer to Oil Consumption Diagnosis in Engine Mechanical.

z

Test for low cylinder compression. Refer to Engine Compression Test in
Engine Mechanical.

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Inspect for incorrect basic engine parts, including the following:

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The camshaft - Refer to Camshaft and Bearings Cleaning and
Inspection in Engine Mechanical.

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The cylinder heads - Refer to Cylinder Head Cleaning and Inspection
in Engine Mechanical.

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The pistons, etc. - Refer to Piston, Connecting Rod, and Bearings
Cleaning and Inspection in Engine Mechanical.

z

Inspect for excessive crankshaft endplay that will cause the crankshaft position
(CKP) sensor reluctor wheel to move out of alignment with the CKP sensor.
Refer to Crankshaft and Bearings Cleaning and Inspection in Engine
Mechanical. This could result in any of the following conditions:

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A no start

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A start and stall

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Erratic performance

Additional
Inspections

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Inspect the exhaust system for possible restrictions. Perform the following:

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Inspect the exhaust system for damaged or collapsed pipes.

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Inspect the mufflers for heat distress or internal failure.

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Inspect for plugged catalytic converters. Refer to Restricted Exhaust in
Engine Exhaust.

z

Inspect the transmission torque converter clutch (TCC) for proper operation.
Refer to Diagnostic Starting Point - Automatic Transmission in Automatic
Transmission - 4L60-E.

Inspection/Tests

Action

DEFINITION: A mild to severe ping, usually worse under acceleration. The engine makes sharp metallic
knocks that change with throttle opening.
Preliminary
Inspections

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Refer to Important Preliminary Inspections Before Starting in Symptoms -
Engine Controls .

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Search for bulletins.

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Verify that the powertrain control module (PCM) grounds are clean, tight, and
in the proper locations. Refer to Power and Grounding Component Views in
Wiring Systems and Engine Controls Schematics .

z

If there are no engine mechanical faults, fill the fuel tank with a known high
quality fuel that meets the vehicles minimum octane requirements. Road test

2004 Hummer H2

2004 ENGINE PERFORMANCE Engine Controls (Troubleshooting) - 4.8L, 5.3L, and 6.0L - Hummer H2

the vehicle and re-evaluate the vehicles performance.

Fuel System

z

Inspect for incorrect fuel pressure. Refer to Fuel System Diagnosis .

z

Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-
Fuel Diagnosis (without Special Tool and E85) or Alcohol/Contaminants-
in-Fuel Diagnosis (with Special Tool) .

z

Inspect for the following conditions that may cause the engine to run lean:

{

Water intrusion in the heated oxygen sensor (HO2S) connector

{

An exhaust leak between the HO2S and the engine - Refer to Exhaust
Leakage in Engine Exhaust.

{

Vacuum leaks

{

Incorrect fuel pressure - Refer to Fuel System Diagnosis .

{

Restricted fuel injectors - Refer to Fuel Injector Balance Test with
Special Tool or Fuel Injector Balance Test with Tech 2 .

{

An inaccurate mass air flow (MAF) sensor

{

Fuel contamination - Refer to Alcohol/Contaminants-in-Fuel
Diagnosis (without Special Tool and E85) or Alcohol/Contaminants-
in-Fuel Diagnosis (with Special Tool) .

{

Vacuum hoses that are split, kinked, or improperly connected

NOTE:

Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and
Notices.

Ignition System

Verify that the spark plugs are of the proper heat range. Refer to Spark Plug
Inspection .

Engine Cooling
System

Inspect for obvious overheating problems:

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Low engine coolant - Refer to Loss of Coolant in Engine Cooling for the type
and amount of engine coolant to be used.

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Restricted air flow to the radiator or restricted coolant flow through the
radiator.

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Inoperative cooling fan - Refer to Fan Clutch Diagnosis in Engine Cooling.

Engine
Mechanical

Inspect for the following engine mechanical problems:

z

Excessive oil in combustion chamber - Leaking valve seals. Refer to Oil
Consumption Diagnosis in Engine Mechanical.

z

Low cylinder compression - Refer to Engine Compression Test in Engine
Mechanical.

z

Combustion chambers for excessive carbon buildup - Clean the combustion
chamber by using top engine cleaner. Follow the instructions on the can.

z

Inspect for incorrect basic engine parts. Inspect the following:

{

The camshaft - Refer to Camshaft and Bearings Cleaning and

2004 Hummer H2

2004 ENGINE PERFORMANCE Engine Controls (Troubleshooting) - 4.8L, 5.3L, and 6.0L - Hummer H2