Hummer H2. Manual - part 1486

Tech 2 Kit 7000081

 

2004 Hummer H2 

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

  

2004 ENGINE PERFORMANCE

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

ENGINE CONTROLS (TROUBLESHOOTING) 

SYMPTOMS - ENGINE CONTROLS 

Important Preliminary Inspections Before Starting 

Perform Diagnostic System Check - Engine Controls before using the symptom tables, and verify that all of 
the following are true: 

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The powertrain control module (PCM) and malfunction indicator lamp (MIL) are operating correctly.  

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There are no DTCs stored.  

z

The scan tool data is within the normal operating range, refer to Scan Tool Data List .  

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Verify the customer concern and locate the correct symptom in the table of contents. Inspect the items 
indicated under that symptom.  

Visual/Physical Inspection 

Several of the symptom procedures ask for a careful visual and physical inspection. This step is extremely 
important. The visual and physical inspection can lead to correcting a problem without further inspections, and 
can save valuable time. Ensure that: 

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The PCM grounds are clean, tight, and in the proper location.  

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The vacuum hoses are not split or kinked, and properly connected, as shown on the Vehicle Emission 
Control Information label. Inspect thoroughly for any type of leak or restriction.  

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The mass air flow (MAF) sensor is properly installed. The arrows on the plastic portion of the sensor 
must point toward the engine.  

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The air intake ducts are not collapsed or damaged.  

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There are no leaks at the throttle body mounting area, the MAF sensor, or the intake manifold sealing 
surfaces.  

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The ignition wires are not cracked, brittle, or carbon tracked.  

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The engine harness wiring and terminals are properly connected and are not pinched or cut.  

Intermittent 

IMPORTANT: Inspect for improper installation of electrical components if an intermittent 

condition exists. Inspect for aftermarket theft deterrent devices, lights, and 
cellular phones. Verify that no aftermarket equipment is connected to the class 
2 circuit. If you can not locate an intermittent condition, a cellular phone 
communication signal may cause the condition.

 

2004 Hummer H2 

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

  

 

2004 Hummer H2 

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

  

Faulty electrical connections or wiring cause most intermittent problems. Perform a careful visual and physical 
inspection of the suspect connectors for the following conditions: 

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Improperly mated connector halves  

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Terminals that are not seated  

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Terminals that are damaged or improperly formed  

Reform or replace connector terminals in the problem circuit in order to ensure proper contact tension. Refer to 
Connector Repairs in Wiring Systems. Remove the terminal from the connector body in order to inspect for 
poor terminal wire connection. Refer to Testing for Intermittent Conditions and Poor Connections in 
Wiring Systems. 

Road test the vehicle with the DMM connected to the suspected circuit. An abnormal reading that occurs when 
the malfunction occurs is a good indication that there is a malfunction in the circuit being monitored. 

Use a scan tool in order to help detect intermittent conditions. Useful features of the GM Techline scan tool 
include the following: 

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Trigger the Snapshot feature in order to capture and store engine parameters when the malfunction 
occurs. Review this stored information in order to see the specific running conditions that caused the 
malfunction.  

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Freeze Frame/Failure Records can also aid in locating an intermittent condition. Review and capture the 
information in the Freeze Frame/Failure Record associated with the intermittent DTC being diagnosed. 
Drive the vehicle within the conditions that were present when the DTC originally set.  

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Use the Plot Function on the scan tool in order to plot selected data parameters. Review this stored 
information to aid in locating an intermittent problem. Refer to the scan tool Users Guide for more 
information.  

Any of the following may cause an intermittent malfunction indicator lamp (MIL) with no stored DTC: 

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The ignition coils are shorted to a ground or arcing at the ignition wires or the spark plugs.  

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The PCM grounds are loose or dirty. Refer to Engine Controls Schematics .  

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The ignition control (IC) wires are routed too close to the secondary ignition wires, coils, or the generator. 
Ensure that all of the circuits from the PCM to the ignition coils have good connections.  

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There is an open diode across the A/C compressor clutch or any other open diodes.  

Use the following tables when diagnosing a symptom complaint:

IMPORTANT: The problem may or may not turn ON the malfunction indicator lamp (MIL) or 

store a DTC.

IMPORTANT: If the intermittent condition exists as a start and then stall, test for DTCs 

relating to the vehicle theft deterrent system. Test for improper installation of 
electrical options such as lights, cellular phones, etc.

 

2004 Hummer H2 

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

  

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Intermittent Conditions  

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Hard Start  

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Surges/Chuggles  

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Lack of Power, Sluggishness, or Sponginess  

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Detonation/Spark Knock  

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Hesitation, Sag, Stumble  

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Cuts Out, Misses  

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Poor Fuel Economy  

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Poor Fuel Fill Quality  

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Rough, Unstable, or Incorrect Idle and Stalling  

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Dieseling, Run-On  

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Backfire  

INTERMITTENT CONDITIONS 

Intermittent Conditions 

Inspection/Test

Action

DEFINITION: The problem is not currently present but is indicated in DTC History. 
OR 
There is a customer complaint, but the symptom can not currently be duplicated, if the problem is not 
DTC related.
Preliminary

Refer to Symptoms - Engine Controls before starting.

Harness/Connector

Many intermittent open or shorted circuits are affected by harness/connector 
movement that is caused by vibration, engine torque, bumps/rough pavement, etc. 
Test for this type of condition by performing the applicable procedure from the 
following list: 

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Move related connectors and wiring while monitoring the appropriate scan 
tool data.  

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Move related connectors and wiring with the component commanded ON, 
and OFF, with the scan tool. Observe the component operation.  

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With the engine running, move related connectors and wiring while 
monitoring engine operation.  

 
If harness or connector movement affects the data displayed, component/system 
operation, or engine operation, inspect and repair the harness/connections as 
necessary. 
Refer to Electrical Connections or Wiring.

Electrical 
Connections or 
Wiring

Poor electrical connections, terminal tension or wiring problems cause most 
intermittents. Refer to Testing for Intermittent Conditions and Poor 
Connections , Circuit Testing , Connector Repairs , or Wiring Repairs in 

 

2004 Hummer H2 

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