Hummer H2. Manual - part 1344

Fig. 3: View Of Good Fuse & Open (Melted) Fuse
Courtesy of GENERAL MOTORS CORP.

The fuse is the most common method of an automotive wiring circuit protection. Whenever there is an
excessive amount of current flowing through a circuit the fusible element will melt and create an open or
incomplete circuit. Fuses are an one time protection device and must be replaced each time the circuit is
overloaded. To determine if a fuse is open, remove the suspected fuse and examine the element in the fuse for
an open (2). If not broken (1), also check for continuity using a DMM or a continuity tester. If the element is
open or continuity is suspect, replace the fuse with one of equal current rating.

Fuse Types

Current Rating Amperes

Color

Auto Fuses, Mini Fuses

Gray

Violet

Tan

7.5

Brown

Red

Blue

Yellow

White or Natural

Green

Maxi Fuses

Yellow

2004 Hummer H2

2004 ACCESSORIES & EQUIPMENT Wiring Systems - Hummer H2

CIRCUIT PROTECTION - CIRCUIT BREAKERS

A circuit breaker is a protective device that is designed to open the circuit when a current load is in excess of the
rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current
will open the circuit between the circuit breaker terminals. Two types of circuit breakers are used.

Circuit Breaker

This type opens when excessive current passes through it for a period of time. It closes again after a few
seconds, and if the cause of the high current is still present, it will open again. The circuit breaker will
continue to cycle open and closed until the condition causing the high current is removed.

Positive Temperature Coefficient (PTC) Circuit Breaker

This type greatly increases its resistance when excessive current passes through it. The excessive current
heats the PTC device, as the device heats its resistance increases. Eventually the resistance gets so high
that the circuit is effectively open. Unlike the ordinary circuit breaker the PTC unit will not reset until the
circuit is opened, by removing the voltage from its terminals. Once the voltage is removed the circuit
breaker will re-close within a second or 2.

CIRCUIT PROTECTION - FUSIBLE LINKS

Fusible link is wire designed to melt and break continuity when excessive current is applied. It is often located
between or near the battery and starter or electrical center. Use a continuity tester or a DMM at each end of the
wire containing the fusible link in order to determine if it is broken. If broken, it must be replaced with fusible
link of the same gauge size.

Repairing a Fusible Link

Refer to Splicing Copper Wire Using Splice Clips .

WIRING REPAIRS

The Wiring Repairs section contains the following types of wiring repair information. Using these elements
together will make wiring repair faster and easier:

Circuit Protection - Fuses

Light Green

Orange or Amber

Blue

Red

IMPORTANT: Fusible links cut longer than 225 mm (approximately 9 in) will not provide

sufficient overload protection.

2004 Hummer H2

2004 ACCESSORIES & EQUIPMENT Wiring Systems - Hummer H2

Circuit Protection - Circuit Breakers

Circuit Protection - Fusible Links

Repairing Damaged Wire Insulation

Splicing Copper Wire Using Splice Clips

Splicing Copper Wire Using Splice Sleeves

Splicing Twisted or Shielded Cable

Splicing Inline Harness Diodes

Heated Oxygen Sensor (HO2S) Wiring Repairs

SIR/SRS Wiring Repairs

Flat Wire Repairs

REPAIRING DAMAGED WIRE INSULATION

If the conductive portion of the wire is not damaged, locate the problem and apply tape around the wire. If the
damage is more extensive, replace the faulty segment of the wire. Refer to Splicing Copper Wire Using Splice
Clips and follow the instruction to repair the wire.

Wire Size Conversion

FLAT WIRE REPAIRS

HEATED OXYGEN SENSOR (HO2S) WIRING REPAIRS

Tools Required

Metric Wire Sizes (mm 2)

AWG Sizes

0.22

0.35

0.5

0.8

1.0

2.0

3.0

5.0

8.0

13.0

19.0

32.0

50.0

1/0

NOTE:

The flat wire within the flex wiring harness is not serviceable. If an open or short
exists within the flex wiring harness the complete harness must be replaced.

2004 Hummer H2

2004 ACCESSORIES & EQUIPMENT Wiring Systems - Hummer H2

J-38125 Terminal Repair Kit. See Special Tools and Equipment .

Heated Oxygen Sensor (HO2S) Wiring Repairs

If the heated oxygen sensor pigtail wiring, connector, or terminal is damaged the entire oxygen sensor assembly
must be replaced. Do not attempt to repair the wiring, connector, or terminals. In order for the sensor to function
properly it must have a clean air reference. This clean air reference is obtained by way of the oxygen sensor
signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction
of the air reference and degrade oxygen sensor performance.

The following guidelines should be used when servicing the heated oxygen sensor:

Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These
materials may get into the sensor, causing poor performance. Also, the sensor pigtail and harness wires
must not be damaged in such a way that the wires inside are exposed. This could provide a path for
foreign materials to enter the sensor and cause performance problems.

Neither the sensor nor vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could
block the reference air path through the lead wire.

Do not remove or defeat the oxygen sensor ground wire (where applicable). Vehicles that utilize the
ground wire sensor may rely on this ground as the only ground contact to the sensor. Removal of the
ground wire will also cause poor engine performance.

To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle
harness connector.

The engine harness may be repaired using the J-38125 . See Special Tools and Equipment .

SPLICING COPPER WIRE USING SPLICE CLIPS

Tools Required

J-38125 Terminal Repair Kit. See Special Tools and Equipment .

Splicing Copper Wire Using Splice Clips

1. Open the harness.

If the harness is taped, remove the tape.

To avoid wiring insulation damage, use a sewing ripper in order to cut open the harness.

If the harness has a black plastic conduit, pull out the desired wire.

NOTE:

Do not solder repairs under any circumstances as this could result in the air
reference being obstructed.

IMPORTANT: When making a splice in an area that may be exposed to moisture use a crimp

and seal splice sleeve instead of a Splice Clip. Refer to Splicing Copper Wire
Using Splice Sleeves

2004 Hummer H2

2004 ACCESSORIES & EQUIPMENT Wiring Systems - Hummer H2

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