Hummer H2. Manual — part 1342

Fig. 2: Measuring Voltage Drop
Courtesy of GENERAL MOTORS CORP.

1. Set the rotary dial of the DMM to the V (DC) position.

2. Connect the positive lead of the DMM to 1 point of the circuit to be tested.

3. Connect the negative lead of the DMM to the other point of the circuit.

4. Operate the circuit.

5. The DMM displays the difference in voltage between the 2 points.

MEASURING FREQUENCY

The following procedure determines the frequency of a signal.

NOTE:

Refer to Test Probe Notice in Cautions and Notices.

2004 Hummer H2

2004 ACCESSORIES & EQUIPMENT Wiring Systems - Hummer H2

1. Apply power to the circuit.

2. Set the rotary dial of the DMM to the V (AC) position.

3. Connect the positive lead of the DMM to the circuit to be tested.

4. Connect the negative lead of the DMM to a good ground.

5. Press the Hz button on the DMM.

6. The DMM will display the frequency measured.

TESTING FOR CONTINUITY

The following procedures verify good continuity in a circuit.

With a DMM

1. Set the rotary dial of the DMM to the ohm position.

2. Disconnect the power feed (i.e. fuse, control module) from the suspect circuit.

3. Disconnect the load.

4. Press the MIN MAX button on the DMM.

5. Connect one lead of the DMM to one end of the circuit to be tested.

6. Connect the other lead of the DMM to the other end of the circuit.

7. If the DMM displays low or no resistance and a tone is heard, the circuit has good continuity.

With a Test Lamp

1. Remove the power feed (i.e. fuse, control module) from the suspect circuit.

2. Disconnect the load.

3. Connect 1 lead of the test lamp to 1 end of the circuit to be tested.

4. Connect the other lead of the test lamp to battery positive voltage.

5. Connect the other end of the circuit to ground.

6. If the test lamp illuminates (full intensity), then the circuit has good continuity.

TESTING FOR SHORT TO GROUND

IMPORTANT: Connecting the DMM to the circuit before pressing the Hz button will allow the

DMM to autorange to an appropriate range.

NOTE:

Refer to Test Probe Notice in Cautions and Notices.

IMPORTANT: Only use the test lamp procedure on low impedance power and ground

circuits.

NOTE:

Refer to Test Probe Notice in Cautions and Notices.

2004 Hummer H2

2004 ACCESSORIES & EQUIPMENT Wiring Systems - Hummer H2

The following procedures test for a short to ground in a circuit.

With a DMM

1. Remove the power feed (i.e. fuse, control module) from the suspect circuit.

2. Disconnect the load.

3. Set the rotary dial of the DMM to the ohm position.

4. Connect 1 lead of the DMM to 1 end of the circuit to be tested.

5. Connect the other lead of the DMM to a good ground.

6. If the DMM does NOT display infinite resistance (OL), there is a short to ground in the circuit.

With a Test Lamp

1. Remove the power feed (i.e. fuse, control module) from the suspect circuit.

2. Disconnect the load.

3. Connect 1 lead of the test lamp to battery positive voltage.

4. Connect the other lead of the test lamp to 1 end of the circuit to be tested.

5. If the test lamp illuminates, there is a short to ground in the circuit.

Fuse Powering Several Loads

1. Review the system schematic and locate the fuse that is open.

2. Open the first connector or switch leading from the fuse to each load.

3. Connect a DMM across the fuse terminals (be sure that the fuse is powered).

z

When the DMM displays voltage the short is in the wiring leading to the first connector or switch.

z

If the DMM does not display voltage refer to the next step.

4. Close each connector or switch until the DMM displays voltage in order to find which circuit is shorted.

TESTING FOR A SHORT TO VOLTAGE

The following procedure tests for a short to voltage in a circuit.

1. Set the rotary dial of the DMM to the V (DC) position.

2. Connect the positive lead of the DMM to 1 end of the circuit to be tested.

3. Connect the negative lead of the DMM to a good ground.

4. Turn ON the ignition and operate all accessories.

5. If the voltage measured is greater than 1 volt, there is a short to voltage in the circuit.

TESTING FOR INTERMITTENT CONDITIONS AND POOR CONNECTIONS

NOTE:

Refer to Test Probe Notice in Cautions and Notices.

2004 Hummer H2

2004 ACCESSORIES & EQUIPMENT Wiring Systems - Hummer H2

Tools Required

z

J 35616 GM-Approved Terminal Test Kit

z

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

z

J 42675 Flat-Wire Probe Adapter. See Special Tools and Equipment .

Most intermittent conditions are caused by faulty electrical connections or wiring. Inspect for the following
items:

z

Wiring broken inside the insulation

z

Poor connection between the male and female terminal at a connector.

z

Poor terminal to wire connection-Some conditions which fall under this description are poor crimps, poor
solder joints, crimping over the wire insulation rather than the wire itself and corrosion in the wire to
terminal contact area, etc.

z

Wire insulation which is rubbed through-This causes an intermittent short as the bare area touches other
wiring or parts of the vehicle.

z

Refer to Inducing Intermittent Fault Conditions in order to duplicate the conditions required in order
to verify the complaint.

z

Refer to Testing for Electrical Intermittents for test procedures to detect intermittent open, high
resistance, short to ground, and short to voltage conditions.

z

Refer to Scan Tool Snapshot Procedure for advanced intermittent diagnosis.

Testing for Proper Terminal Contact

It is important to test terminal contact at the component and any inline connectors before replacing a suspect
component. Mating terminals must be inspected to ensure good terminal contact. A poor connection between
the male and female terminal at a connector may be the result of contamination or deformation.

Contamination may be caused by the connector halves being improperly connected. A missing or damaged
connector seal, damage to the connector itself, or exposing the terminals to moisture and dirt can also cause
contamination. Contamination, usually in the underhood or underbody connectors, leads to terminal corrosion,
causing an open circuit or intermittently open circuit.

Deformation is caused by probing the mating side of a connector terminal without the proper adapter. Always
use the J 35616 when probing connectors. Other causes of terminal deformation are improperly joining the
connector halves, or repeatedly separating and joining the connector halves. Deformation, usually to the female
terminal contact tang, can result in poor terminal contact causing an open or intermittently open circuit. See
Special Tools and Equipment .

Round Wire Connectors

Follow the procedure below to test terminal contact of Metri-Pack or 56 series terminals. Refer to the J-38125
or the J 38125-4 Instruction Manual for terminal identification. See Special Tools and Equipment .

Follow the procedure below in order to test terminal contact.

2004 Hummer H2

2004 ACCESSORIES & EQUIPMENT Wiring Systems - Hummer H2