Hummer H2. Manual — part 1096

GENERATOR NOISE DIAGNOSIS

Diagnostic Aids

Noise from a generator may be due to electrical or mechanical noise. Electrical noise (magnetic whine) usually
varies with the electrical load placed on the generator and is a normal operating characteristic of all generators.
When diagnosing a noisy generator, it is important to remember that loose or misaligned components around
the generator may transmit the noise into the passenger compartment and that replacing the generator may not
solve the problem.

Generator Noise Diagnosis

4

Operate the system in order to verify the
repair.
Did you correct the condition?

System OK

Go to Step 2

Step

Action

Yes

No

1

Test the generator for proper operation using the Generator Tester. Refer to
Charging System Test (CS/AD/SI Generators) .
Is the generator operating properly?

Go to

Step 2

Go to

Step

11

2

1. Start the engine. Verify that the noise can be heard.

2. Turn OFF the engine.

3. Disconnect the 4-way connector from the generator.

4. Start the engine.

5. Listen for the noise.

Has the noise stopped?

Go to

Step 11

Go to

Step 3

3

Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement in
Engine Controls.Is the action complete?

IMPORTANT:

The replacement PCM must be programmed.

Go to

Step 4

Go to

Step

11

4

Inspect the generator for a loose pulley and/or pulley nut.
Is the generator pulley or pulley nut loose?

Go to

Step 11

Go to

Step 5

5

1. Loosen all of the generator mounting bolts.

2. Tighten the generator mounting bolts to specifications and in the proper

sequence (if necessary). Refer to Generator Replacement .

3. Install the drive belt. Refer to Drive Belt Replacement - Accessory in

Engine Mechanical.

4. Start the engine.

Has the noise decreased or stopped?

System

OK

Go to

Step 6

Inspect the generator for the following conditions:

2004 Hummer H2

2004 ELECTRICAL Engine Electrical - Hummer H2

STARTER SOLENOID DOES NOT CLICK

Starter Solenoid Does Not Click

6

z

Strained or stretched electrical connections.

z

Hoses or other vehicle equipment resting on the generator, (which may
cause the noise to be transmitted into the passenger compartment)

Are any electrical connections pulling on the generator or are any hoses, etc.
resting on the generator?

Go to

Step 7

Go to

Step 8

7

1. Reroute the electrical connections to relieve the tension.

2. Reroute the hoses, etc. away from the generator.

3. Start the engine.

Has the noise decreased or stopped?

System

OK

Go to

Step 8

8

Inspect the drive belt for proper tension. Refer to Drive Belt Tensioner Diagnosis
in Engine Mechanical.
Is the drive belt loose?

Go to

Step 9

Go to

Step

10

9

1. Replace the drive belt tensioner. Refer to Drive Belt Tensioner

Replacement - Accessory in Engine Mechanical.

2. Start the engine.

Has the noise decreased or stopped?

System

OK

Go to

Step

11

10

Compare the vehicle with a known good vehicle.
Do both vehicles make the same noise?

System

OK

Go to

Step

11

11

Replace the generator. Refer to Generator Replacement .Has the noise decreased
or stopped?

IMPORTANT:

If no definite generator problems were found, be sure that all other possible
sources of objectionable noise are eliminated before replacing the generator.
Replacing the generator may not change the noise level if the noise is a
normal characteristic of the generator or the generator mounting.

Go to

Step 12

-

12

Operate the system in order to verify the repair.
Did you correct the condition?

System

OK

Go to

Step 2

Step

Action

Yes

No

Schematic Reference:Starting and Charging Schematics

1

Did you preform the Engine Electrical Diagnostic System
Check?

Go to

Diagnostic

System Check

- Engine

2004 Hummer H2

2004 ELECTRICAL Engine Electrical - Hummer H2

Go to Step 2

Electrical

2

Turn the ignition switch to the START position.
Does the engine crank?

Go to Testing for

Intermittent

Conditions and Poor

Connections in

Wiring Systems

Go to Step 3

3

Turn the ignition switch to the START position.
Does the starter motor relay click?

Go to Step 11

Go to Step 4

4

1. Turn OFF the ignition.

2. Disconnect the powertrain control module (PCM)

harness connector.

3. Connect a test lamp between the Crank Voltage

circuit of the PCM harness and a good ground.

4. With the transmission in park, turn the ignition

switch to the START position.

Does the test light illuminate?

Go to Step 7

Go to Step 5

5

Inspect for poor connections at the PCM connector,
Underhood Fuse Block or ignition switch harness
connector. Refer to Testing for Intermittent Conditions
and Poor Connections and Connector Repairs in Wiring
Systems.
Did you find and correct the condition?

Go to Step 29

Go to Step 6

6

Test the supply voltage circuit of the crank voltage circuit
and Crank fuse for an open or high resistance. Refer to
Testing for Intermittent Conditions and Poor
Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?

Go to Step 29

Go to Step 27

7

1. Turn OFF the ignition.

2. Disconnect the PCM harness connector.

3. Connect a test lamp between the starter enable relay

control circuit of the PCM harness and a good
ground.

4. Turn the ignition to the START position.

Does the test lamp illuminate?

Go to Step 19

Go to Step 8

8

1. Remove the starter motor relay.

2. Connect a test light from the supply voltage circuit

of the starter motor relay coil circuit to ground.

3. With the transmission in park, turn the ignition

switch to the START position.

Does the test light illuminate?

Go to Step 9

Go to Step 10

2004 Hummer H2

2004 ELECTRICAL Engine Electrical - Hummer H2

9

1. Connect a test light from the supply voltage circuit

of the starter motor relay coil circuit to the control
circuit of the starter motor relay coil circuit.

2. With the transmission in park, turn the ignition

switch to the START position.

Does the test light illuminate?

Go to Step 17

Go to Step 14

10

1. Turn OFF the ignition.

2. Disconnect the park neutral position (PNP) switch.

Refer to Park/Neutral Position Switch
Replacement in Automatic Transmission - 4L60-
E/4L65-E.

3. Turn ON the ignition, with the engine OFF.

4. Connect a 10-amp fused jumper between the starter

motor relay coil control circuits of the PNP switch.

5. With the transmission in PARK, turn the ignition

switch to the START position.

Does the test lamp illuminate?

Go to Step 18

Go to Step 15

11

1. Turn OFF the ignition.

2. Disconnect the starter motor relay.

3. Connect a test lamp between the battery positive

voltage circuit of the starter motor relay switch
circuit and a good ground.

Does the test lamp illuminate?

Go to Step 12

Go to Step 23

12

Connect a 30-amp fused jumper between the battery
positive voltage circuit of the starter motor relay switch
circuit and the supply voltage circuit of the starter
solenoid.
Does the engine crank?

Go to Step 17

Go to Step 13

13 Does the fuse in the jumper open?

Go to Step 24

Go to Step 16

14

Test the control circuit of the starter motor relay for an
open or high resistance. Refer to Circuit Testing and
Wiring Repairs in Wiring Systems.
Did you find and correct the condition?

Go to Step 29

Go to Step 25

15

Test the supply voltage circuit of the starter motor relay
coil circuit for an open or high resistance. Refer to Circuit
Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?

Go to Step 29

Go to Step 21

16

Test the supply voltage circuit of the starter solenoid for an
open or high resistance. Refer to Circuit Testing and
Wiring Repairs in Wiring Systems.

2004 Hummer H2

2004 ELECTRICAL Engine Electrical - Hummer H2