Hummer H2. Manual - part 1195

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