Hummer H2. Manual - part 1193

16. Repeat the parasitic current drain test procedure after any repair has been completed.  

17. When the cause of the excessive current draw has been located and repaired, remove the meter and the 

parasitic draw test switch and terminal adapters.  

18. Connect the negative cable to the battery negative terminal. Refer to Battery Negative Cable 

Disconnect/Connect Procedure (Single Battery) .  

BATTERY COMMON CAUSES OF FAILURE 

A battery is not designed to last forever. With proper care, however, the battery will provide years of good 
service. If the battery tests good but still fails to perform well, the following are some of the more common 
causes: 

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A vehicle accessory was left on overnight.  

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The driving speeds have been slow with frequent stops with many electrical accessories in use, 
particularly air conditioning, headlights, wipers, heated rear window, cellular telephone, etc.  

z

The electrical load has exceeded the generator output, particularly with the addition of aftermarket 
equipment.  

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Existing conditions in the charging system, including the following possibilities: 

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A slipping belt  

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A bad generator  

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The battery has not been properly maintained, including a loose battery hold down or missing battery 
insulator if used.  

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There are mechanical conditions in the electrical system, such as a short or a pinched wire, attributing to 
power failure. Refer to General Electrical Diagnosis Procedures in Wiring Systems.  

Electrolyte Freezing 

The freezing point of electrolyte depends on its specific gravity. A fully charged battery will not freeze until the 
ambient temperature gets below -54° C (-65° F). However, a battery with a low state of charge may freeze at 
temperatures as high as -7° C (+20° F). Since freezing may ruin a battery, the battery should be protected 
against freezing by keeping it properly charged. As long as the green eye is visible in the hydrometer, the 
freezing point of the battery will be somewhere below -32° C (-25° F). 

Battery Protection During Vehicle Storage 

Certain devices on the vehicle maintain a small continuous current drain on the battery. A battery that is not 
used for an extended period of time will discharge. Eventually permanent damage will result. Discharged 
batteries will also freeze in cold weather. Refer to Battery Inspection/Test (Non-HP2) . 

In order to maintain a battery state of charge while storing the vehicle for more than 30 days: 

IMPORTANT: If a green dot is not visible in the hydrometer, charge the battery. Refer to 

Battery Charging .

 

2004 Hummer H2 

2004 ELECTRICAL Engine Electrical - Hummer H2

  

1. Ensure that the green dot is visible in the built-in hydrometer. 

2. Disconnect the battery ground to protect the battery from discharge by parasitic current drains.  

When the battery cannot be disconnected: 

1. Maintain a high state of charge.  

2. Establish a regular schedule for recharging the battery every 20-45 days.  

A battery that has remained in a discharged state for a long period of time is difficult to recharge or may be 
permanently damaged. 

JUMP STARTING IN CASE OF EMERGENCY (NON HP2) 

This vehicle has a 12-volt positive, negative ground electrical system. Do not try to jump start a vehicle, if you 
are unsure of the other vehicle's positive voltage or ground position. The booster battery and the discharged 
battery should be treated carefully when using jumper cables. 

1. Position the vehicle with the booster battery so that the jumper cables will comfortably reach the battery 

of the other vehicle. 

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Do not let the 2 vehicles touch.  

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Make sure that the jumper cables do not have loose clamps or missing insulation.  

CAUTION: Refer to Battery Disconnect Caution in Cautions and Notices.

CAUTION: Batteries produce explosive gases. Batteries contain corrosive acid. 

Batteries supply levels of electrical current high enough to cause burns. 
Therefore, in order to reduce the risk of personal injury while working near 
a battery, observe the following guidelines: 

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Always shield your eyes.  

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Avoid leaning over the battery whenever possible.  

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Do not expose the battery to open flames or sparks.  

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Do not allow battery acid to contact the eyes or the skin. 

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Flush any contacted areas with water immediately and 
thoroughly.  

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Get medical help.  

NOTE:

This vehicle has a 12 volt, negative ground electrical system. Make sure the 
vehicle or equipment being used to jump start the engine is also 12 volt, 
negative ground. Use of any other type of system will damage the vehicle's 
electrical components.

 

2004 Hummer H2 

2004 ELECTRICAL Engine Electrical - Hummer H2

  

2. Perform the following steps on both vehicles: 

1. Place the automatic transmission in PARK.  

2. Block the wheels.  

3. Set the parking brake.  

4. Turn off all electrical loads that are not needed. Leave the hazard flashers ON.  

5. Turn OFF the ignition switch.  

 

2004 Hummer H2 

2004 ELECTRICAL Engine Electrical - Hummer H2

  

Fig. 6: Connecting Battery Terminal Jumpers 
Courtesy of GENERAL MOTORS CORP. 

IMPORTANT: Some vehicles have a battery remote positive stud. ALWAYS use the 

battery remote positive stud in order to give or to receive a jump start. 
Consult the vehicle's owner's manual for proper connections.

 

2004 Hummer H2 

2004 ELECTRICAL Engine Electrical - Hummer H2