Hummer H2. Manual — part 1908

Fig. 4: Identifying Ignition Switch Harness Connector Terminals
Courtesy of GENERAL MOTORS CORP.

2004 Hummer H2

2004 STARTING & CHARGING SYSTEMS Starters - H2

Fig. 5: Identifying Park/Neutral Switch Harness Connector Terminals
Courtesy of GENERAL MOTORS CORP.

DIAGNOSTIC STARTING POINT - ENGINE ELECTRICAL

Begin the system diagnosis with the Diagnostic System Check - Engine Electrical. See DIAGNOSTIC
SYSTEM CHECK - ENGINE ELECTRICAL . The Diagnostic System Check will provide the following
information:

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The identification of the control module(s) which command the system.

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The ability of the control module(s) to communicate through the serial data circuit.

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The identification of any stored diagnostic trouble codes (DTCs) and their status.

The use of the DIAGNOSTIC SYSTEM CHECK - ENGINE ELECTRICAL will identify the correct
procedure for diagnosing the system and where the procedure is located.

DIAGNOSTIC SYSTEM CHECK - ENGINE ELECTRICAL

1. Did you perform the Battery Inspection/Test? If yes, go to next step. If no, go to BATTERY

INSPECTION/TEST (NON-HP2) .

2004 Hummer H2

2004 STARTING & CHARGING SYSTEMS Starters - H2

2. Install a scan tool. Does the scan tool power up? If yes, go to step 4 . If no, go to SCAN TOOL DOES

NOT POWER UP .

3.

Access the Class 2 Power Mode in the Diagnostic Circuit Check on the scan tool. Rotate the ignition
switch through all positions while observing the ignition switch power mode parameter. Does the ignition
switch parameter reading match the ignition switch position for all switch positions? If yes, go to next
step. If no, go to POWER MODE MISMATCH .

4. Turn ON the ignition, with the engine OFF. Attempt to communicate with each module on the class 2

serial data circuit. If using a Tech 2, obtain this information using the Class 2 Message Monitor feature.
Does the scan tool communicate with any module on the class 2 serial data circuit? If yes, go to next step.
If no, go to Scan Tool Does Not Communicate with Class 2 Device in BODY CONTROL MODULES

5. Select the Display DTCs function for each module. If using a Tech 2, use the Class 2 DTC Check feature

in order to determine which modules have DTCs set. Record all of the displayed DTCs the DTC status
and the module which set the DTC. Does the scan tool display any DTCs? If yes, go to next step. If no,
go to SYMPTOMS - ENGINE ELECTRICAL .

6. Does the scan tool display any DTC beginning with "U"? If yes, go to Diagnostic Trouble Code (DTC)

List. If no, go to next step.

7. Does the scan tool display any DTC beginning with "P"? If yes, go to Powertrain DTC list in Engine

Controls. If no, go to next step.

8. Does the scan tool display any DTC beginning with "B"? If yes, go to Diagnostic Trouble Code (DTC)

List.

BATTERY INSPECTION/TEST (NON-HP2)

Diagnostic Aids

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If testing the vehicle with the battery cables still connected, wiggle the J-42000 clips on the terminal bolt.
This may cut through any coating or through any oxidation that may be present on the bolt. Even new
bolts contain a protective coating that may insulate or cause a resistance in the test circuit.

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If correct connections to the battery terminal bolts in the vehicle are in doubt, perform the following
steps:

A. Disconnect the negative battery cable.

B. Disconnect the positive battery cable.

C. Install the test adapters on the terminals.

D. Follow the instructions for testing a removed battery.

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If the tester displays a REPLACE BATTERY or BAD CELL-REPLACE result for a battery tested in the
vehicle with the battery cables connected, perform the following steps:

NOTE:

The engine may start during the following step. Turn OFF the engine as
soon as you have observed the Crank power mode.

NOTE:

Follow these instructions in order to avoid an incorrect diagnosis because of
connections:

2004 Hummer H2

2004 STARTING & CHARGING SYSTEMS Starters - H2

A. Disconnect the negative battery cable.

B. Disconnect the positive battery cable.

C. Install the tester adapters.

D.

Follow the instructions for testing a removed battery.

E. Replace the battery only if the second test shows a REPLACE BATTERY or BAD CELL-

REPLACE result. Use the test code from the second test for any warranty purposes.

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Use the correct terminal adapters. Do not use any common bolts or a combination of bolts, of nuts, and of
washers as adapters when testing the battery. Use the test adapters that are provided with the J-42000 or
GM P/N 12303040 terminal adapters. If the adapters that are provided with the J-42000 require
replacement, use GM P/N 12303040. Any other adapter may not contact the correct areas of the battery
terminal, causing a resistance that may result in an invalid battery test result.

Diagnostic Procedures

1. Inspect the battery for a cracked, broken, or damaged case, which may be indicated by battery acid

leakage. Is the battery OK? If yes, go to next step. If no, go to step 19 .

2. Compare the Cold Cranking Amperage (CCA) and Reserve Capacity (RC) of the battery to the original

battery or Original Equipment (OE) specification. Refer to BATTERY USAGE . Does the battery meet
or exceed the specifications? If yes, go to next step. If no, go to step 19 .

3. Does the hydrometer display a yellow dot? If yes, go to next step. If no, go to step 5 .

4. Tap the hydrometer lightly on top with the handle of a small screwdriver in order to dislodge any air

bubbles inside the battery. Does the hydrometer still display a yellow dot? If yes, go to step 19 . If no, go
to next step.

5. Turn OFF the ignition. Attempt to rotate the negative battery cable connector clockwise with light finger

pressure. Does the negative connector rotate? If yes, go to next step. If no, go to step 7 .

6. Use a torque wrench in order to verify the torque to loosen the negative battery terminal bolt. Is the torque

above the specified value? 10 N.m (88 lb in). If yes, go to step 8 . If no, go to next step.

NOTE:

Important: Always write the test code displayed by the tester on the
repair order for any warranty purposes. The number is a unique code
that describes the test data for a particular battery at a particular
time. The test code may occasionally repeat when you retest the
same battery. More often, each test will result in a different code. Use
the test code from the second, or Out of Vehicle test.

CAUTION: Before servicing any electrical component, the ignition key must be in the

OFF or LOCK position and all electrical loads must be OFF, unless
instructed otherwise in these procedures. If a tool or equipment could
easily come in contact with a live exposed electrical terminal, also
disconnect the negative battery cable. Failure to follow these precautions
may cause personal injury and/or damage to the vehicle or its
components.

2004 Hummer H2

2004 STARTING & CHARGING SYSTEMS Starters - H2