Hummer H2. Manual - part 1487

Wiring Systems to perform the following inspections: 

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Inspect for poor mating of the connector halves, or terminals improperly 
seated in the connector body.  

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Inspect for improperly formed or damaged terminals. Test for poor terminal 
tension.  

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Inspect for poor terminal to wire connections including terminals crimped 
over insulation. This requires removing the terminal from the connector 
body.  

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Inspect for corrosion/water intrusion. Pierced or damaged insulation can 
allow moisture to enter the wiring. The conductor can corrode inside the 
insulation, with little visible evidence. Look for swollen and stiff sections 
of wire in the suspect circuits.  

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Inspect for wires that are broken inside the insulation.  

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Inspect the harness for pinched, cut or rubbed through wiring.  

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Ensure that the wiring does not come in contact with hot exhaust 
components.  

Control Module 
Power and Grounds 
Component Power 
and Grounds

Poor power or ground connections can cause widely varying symptoms. 

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Test all control module power supply circuits. Many vehicles have multiple 
circuits supplying power to the control module. Other components in the 
system may have separate power supply circuits that may also need to be 
tested. Inspect connections at the module/component connectors, fuses, and 
any intermediate connections between the power source and the 
module/component. A test lamp or a DMM may indicate that voltage is 
present, but neither tests the ability of the circuit to carry sufficient current. 
Ensure that the circuit can carry the current necessary to operate the 
component. Refer to Circuit Testing and Power Distribution Schematics 
in Wiring Systems.  

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Test all control module ground and system ground circuits. The control 
module may have multiple ground circuits. Other components in the system 
may have separate grounds that may also need to be tested. Inspect grounds 
for clean and tight connections at the grounding point. Inspect the 
connections at the component and in splice packs, where applicable. Ensure 
that the circuit can carry the current necessary to operate the component. 
Refer to Circuit Testing and Ground Distribution Schematics in Wiring 
Systems.  

Temperature 
Sensitivity

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An intermittent condition may occur when a component/connection reaches 
normal operating temperature. The condition may occur only when the 
component/connection is cold, or only when the component/connection is 
hot.  

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Freeze Frame, Failure Records, Snapshot, or Vehicle Data Recorder data 
may help with this type of intermittent condition, where applicable.  

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If the intermittent is related to heat, review the data for a relationship with 

 

2004 Hummer H2 

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

  

the following: 

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High ambient temperatures  

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Underhood/engine generated heat  

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Circuit generated heat due to a poor connection, or high electrical 
load  

{

Higher than normal load conditions, towing, etc.  

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If the intermittent is related to cold, review the data for the following: 

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Low ambient temperatures - In extremely low temperatures, ice may 
form in a connection or component. Test for water intrusion.  

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The condition only occurs on a cold start.  

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The condition goes away when the vehicle warms up.  

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Information from the customer may help to determine if the trouble follows 
a pattern that is temperature related.  

Electromagnetic 
Interference (EMI) 
and Electrical Noise

Some electrical components/circuits are sensitive to EMI or other types of 
electrical noise. Inspect for the following conditions: 

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A misrouted harness that is too close to high voltage/high current devices 
such as secondary ignition components, motors, generator etc. These 
components may induce electrical noise on a circuit that could interfere 
with normal circuit operation.  

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Electrical system interference caused by a malfunctioning relay, or a 
powertrain control module (PCM) driven solenoid or switch. These 
conditions can cause a sharp electrical surge. Normally, the problem will 
occur when the malfunctioning component is operating.  

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Improper installation of non-factory or aftermarket add on accessories such 
as lights, 2-way radios, amplifiers, electric motors, remote starters, alarm 
systems, cell phones, etc. These accessories may lead to an emission related 
OBD II failure while in use, but do not fail when the accessories are not in 
use. Refer to Checking Aftermarket Accessories in Wiring Systems.  

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Test for an open diode across the A/C compressor clutch and for other open 
diodes. Some relays may contain a clamping diode.  

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Test the generator for a bad rectifier bridge that may be allowing AC noise 
into the electrical system. Refer to Diagnostic System Check - Engine 
Electrical in Engine Electrical.  

Incorrect PCM 
Programming

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There are only a few situations where reprogramming a PCM is 
appropriate: 

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A new service PCM is installed.  

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A PCM from another vehicle is installed.  

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Revised software/calibration files have been released for this vehicle. 

IMPORTANT:

DO NOT re-program the PCM with the SAME software/calibration files 

 

2004 Hummer H2 

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

  

HARD START 

Hard Start 

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Verify that the PCM contains the correct software/calibration. If incorrect 
programming is found, reprogram the PCM with the most current 
software/calibration. Refer to Service Programming System (SPS) in 
Programming.  

that are already present in the PCM. This is not an effective repair for 
any type of driveability problem.

Duplicating Failure 
Conditions

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If none of the previous tests are successful, attempt to duplicate and/or 
capture the failure conditions.  

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Freeze Frame/Failure Records data, where applicable, contains the 
conditions that were present when the DTC set. 

1. Review and record Freeze Frame/Failure Records data  

2. Clear the DTCs using the scan tool.  

3. Turn the key to OFF and wait 15 seconds.  

4. Operate the vehicle under the same conditions that were noted in 

Freeze Frame/Failure Records data, as closely as possible. The 
vehicle must also be operating within the Conditions for Running the 
DTC. Refer to Conditions for Running the DTC in the supporting 
text of the DTC being diagnosed.  

5. Monitor DTC Status for the DTC being tested. The scan tool will 

indicate Ran, when the enabling conditions have been satisfied long 
enough for the DTC to run. The scan tool will also indicate whether 
the DTC passed or failed.  

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An alternate method is to drive the vehicle with the DMM connected to a 
suspected circuit. An abnormal reading on the DMM when the problem 
occurs, may help you locate the problem.  

Scan Tool Snapshot

The scan tool can be set up to take a Snapshot of the parameters available via 
serial data. The Snapshot function records live data over a period of time. The 
recorded data can be played back and analyzed. The scan tool can also graph 
parameters singly or in combinations of parameters for comparison. The Snapshot 
can be triggered manually at the time the symptom is noticed, or set up in advance 
to trigger when a DTC sets. 
An abnormal value captured in the recorded data may point to a system or 
component that needs to be investigated further. 
Refer to the scan tool user instructions for more information on the Snapshot 
function.

Vehicle Data 
Recorder

The J 42598 Vehicle Data Recorder is connected to the data link connector 
(DLC) and sent with the customer. The J 42598 captures data for later retrieval 
and analysis by the technician. Refer to the vehicle data recorder user instructions 
for more information.

 

2004 Hummer H2 

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

  

Inspection/Test

Action

DEFINITION: Engine cranks OK, but does not start for a long time. Does eventually run, or may start 
but immediately dies.
Preliminary

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

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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 .  

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Search for bulletins.  

Sensor/System

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Verify that the engine coolant temperature (ECT) sensor is not shifted in value. 
Connect a scan tool. Compare the engine coolant temperature to the intake air 
temperature (IAT) on a cold engine. The ECT and IAT sensor values should be 
within +/- 3°C (5°F) of each other. If the ECT sensor is out of range with the IAT 
sensor, measure the resistance of the ECT sensor. Refer to Temperature vs 
Resistance for resistance specifications. 

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Inspect the mass air flow (MAF) sensor installation. A MAF sensor that is 
incorrectly installed may cause a hard start. Install the MAF in the proper 
direction. Refer to Mass Air Flow (MAF)/Intake Air Temperature (IAT) 
Sensor Replacement .  

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Inspect the camshaft position (CMP) sensor for proper mounting and/or a bad 
connection. An extended crank occurs if the PCM does not receive a CMP 
signal.  

IMPORTANT:

The embossed arrows on the MAF sensor indicate the direction of the intake 
air flow. The arrows must point toward the engine.

Fuel System

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Inspect the fuel pump relay operation. The fuel pump should turn ON for 2 
seconds when you turn ON the ignition. Refer to Fuel Pump Electrical Circuit 
Diagnosis .  

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

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

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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) .  

Ignition System

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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 
circuits and the fuel injector circuits for an intermittent short to ground. Refer to 
Circuit Testing in Wiring Systems. Replace the fuse.  

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

 

2004 Hummer H2 

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