Hummer H2. Manual - part 1150

Turn OFF the ignition. Connect the red lead of the J-41450-B Universal CS Generator Test Harness to the 
generator output terminal. Connect the black lead of the J-41450-B to the metal generator housing. Does 
the green POWER lamp on the tester illuminate? If yes, go to step 6 . If no, go to next step.  

4. Measure the voltage from the output terminal of the generator to the generator metal housing. Does the 

voltage measure equal to the specified value? 12.0 V. If yes, go to step 14 . If no, go to next step.  

5. Measure the voltage from the output terminal of the generator to the battery negative terminal. Does the 

voltage measure equal to the specified value? 12.0 V. If yes, go to step 12 . If no, go to step 11 .  

6.  

Turn OFF completely the load tool before connecting or disconnecting a carbon pile load tester to the 
battery. Otherwise, sparking at the terminals could cause battery gasses to explode. Connect a carbon pile 
tester to the vehicle. Connect an inductive ammeter to the output circuit of the generator. Disconnect the 
generator harness connector. Locate the matching harness connector on the J-41450-B , and connect the 
connector to the generator. Does the red DIAGNOSTIC lamp on the tester illuminate? If yes, go to next 
step. If no, go to step 13 .  

7. Start the engine and allow it to idle for 30 seconds. Increase the engine speed to 2,500 RPM. Does the red 

DIAGNOSTIC lamp on the tester illuminate? If yes, go to step 15 . If no, go to next step.  

8.  

Maintain the engine speed at 2,500 RPM. Turn ON the load of the carbon pile tester and increase the load 
until the generator output is equal to the Load Test value given in Generator Usage. See GENERATORS 
& REGULATORS . Does the red DIAGNOSTIC lamp on the tester illuminate? If yes, go to step 15 . If 
no, go to next step.  

9. Maintain the engine speed at 2,500 RPM and continue to operate the generator at the load test value. 

Measure the voltage drop from the output terminal of the generator to the positive terminal on the battery. 
Does the voltage measure greater than the specified value? 0.5 V. If yes, go to step 11 . If no, go to next 
step.  

10. Maintain the engine speed at 2,500 RPM and continue to operate the generator at the load test value. 

Measure the voltage drop from the battery negative terminal to the metal housing of the generator. Does 
the voltage measure greater than the specified value? 0.5 V. If yes, go to step 12 . If no, go to step 16 .  

11. Repair the high resistance or an open in the output circuit of the generator. Did you complete the repair? 

If yes, go to step 16 .  

12. Repair the high resistance or open in the ground circuit of the generator. Did you complete the repair? If 

yes, go to step 16 .  

13. Disconnect the J-41450-B tester harness connector from the generator, but leave the alligator clips 

connected so that the green POWER lamp remains illuminated. Connect a jumper lead, with an in-line 
100-ohm resistor between the J-41450-B tester harness connector terminal B of the generator and a good 

NOTE:

The green POWER lamp of the tester should remain illuminated while the 
tester is being used. 

NOTE:

Ensure that all generator output circuit wires pass through the inductive 
probe. 

NOTE:

If the generator is not capable of producing the Load Test amps, operate 
the generator at it's maximum possible output. 

 

2004 Hummer H2 

2004 STARTING & CHARGING SYSTEMS Starters - H2

  

ground. Does the red DIAGNOSTIC lamp illuminate? If yes, go to step 15 . If no, go to next step.  

14. There is a problem with the J-41450-B. Refer to the manufacturers instructions, how to test the J-41450-B 

for proper operation. Has the J-41450-B tester been replaced? If yes, go to step 3 .  

15. Replace the generator. Refer to Generator Replacement in GENERATORS & REGULATORS . Did 

you complete the replacement? If yes, go to next step.  

16. Operate the vehicle in order to verify the repair. Did you correct the condition? If yes, system OK. If no, 

go to step 2 .  

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.  

Diagnostic Procedures 

1. Test the generator for proper operation using the Generator Tester. Refer to GENERATORS & 

REGULATORS . Is the generator operating properly? If yes, go to next step. If no, go to step 11 .  

2. Start the engine. Verify that the noise can be heard. Turn OFF the engine. Disconnect the 4-way 

connector from the generator. Start the engine. Listen for the noise. Has the noise stopped? If yes, go to 
step 11 . If no, go to next step.  

3.  

Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement. Is the action complete? If 
yes, go to next step. If no, go to step 11 .  

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

yes, go to step 11 . If no, go to next step.  

5. Loosen all of the generator mounting bolts. Tighten the generator mounting bolts to specifications and in 

the proper sequence (if necessary). Refer to Generator Replacement in GENERATORS & 
REGULATORS . Install the drive belt. Start the engine. Has the noise decreased or stopped? If yes, 
system OK. If no, go to next step.  

6. Inspect the generator for the following conditions: Strained or stretched electrical connections. 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? If yes, go to next step. If no, go to step 8 .  

7. Reroute the electrical connections to relieve the tension. Reroute the hoses, etc. away from the generator. 

Start the engine. Has the noise decreased or stopped? If yes, system OK. If no, go to next step.  

8. Inspect the drive belt for proper tension. If yes, go to next step. If no, go to step 10 .  

9. Replace the drive belt tensioner. Start the engine. Has the noise decreased or stopped? If yes, system OK. 

NOTE:

The replacement PCM must be programmed. 

 

2004 Hummer H2 

2004 STARTING & CHARGING SYSTEMS Starters - H2

  

If no, go to step 11 .  

10. Compare the vehicle with a known good vehicle. Do both vehicles make the same noise? If yes, system 

OK. If no, go to next step.  

11.  

Replace the generator. Refer to Generator Replacement in GENERATORS & REGULATORS . Has 
the noise decreased or stopped? If yes, go to next step.  

12. Operate the system in order to verify the repair. Did you correct the condition? If yes, system OK. If no, 

go to step 2 .  

STARTER NOISE DIAGNOSIS 

Diagnostic Aids 

z

Inspect the flywheel ring gear for damage or unusual wear.  

z

Shim the starter if applicable.  

z

In order to add pinion to ring gear clearance a full size shim must be used. Do not shim only 1 starter 
mounting bolt. There are 3 shims available in different shapes for clearance. All are 1 mm (0.039 in) 
thick.  

Diagnostic Procedures 

1. Did you perform the Engine Electrical Diagnostic System Check? If yes, go to next step. If no, go to 

DIAGNOSTIC SYSTEM CHECK - ENGINE ELECTRICAL .  

2. Start the engine. Does the starter operate normally? If yes, problem is intermittent. If no, go to next step.  

3. Start the engine while listening to the starter motor turn. Is there a loud "whoop", it may sound like a siren 

if the engine is revved while the starter is engaged after the engine starts, but while the starter is still held 
in the engaged position? If yes, go to step 6 . If no, go to next step.  

4. Do you hear a "rumble", a "growl", or, in some cases, a "knock" as the starter is coasting down to a stop 

after starting the engine? If yes, go to step 7 . If no, go to next step.  

5. This is often diagnosed as a starter drive gear hang-in or a weak solenoid. When the engine is cranked, do 

you hear a high-pitched whine after the engine cranks and starts normally? If yes, go to step 8 . If no, go 
to step 7 .  

6. Inspect the flywheel ring gear for a chipped gear teeth, missing gear teeth or milled teeth. Is the flywheel 

bent, or does it have damaged teeth? If yes, go to step 9 . If no, go to step 10 .  

7. Remove the starter motor. Refer to STARTER MOTOR REPLACEMENT . Inspect the starter motor 

bushings and clutch gear. Does the clutch gear have chipped or milled teeth or worn bushings? If yes, go 
to step 10 . If no, go to next step.  

8. Shim the starter motor away from the flywheel by adding shims between the starter motor and the engine 

NOTE:

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. 

 

2004 Hummer H2 

2004 STARTING & CHARGING SYSTEMS Starters - H2

  

block one at a time. Flywheel runout may make this noise appear to be intermittent. Did you complete the 
repair? If yes, go to step 11 .  

9. Replace the flywheel. Refer to Engine Mechanical. Did you complete the replacement? If yes, go to step 

11 .  

10. Replace the starter motor. Refer to STARTER MOTOR REPLACEMENT . Did you complete the 

replacement? If yes, go to next step.  

11. Operate the system in order to verify the repair. Did you correct the condition? If yes, system OK. If no, 

go to step 3 .  

BATTERY DIAGNOSIS & SERVICING 

BATTERY CHARGING 

z

Use J-42000 Battery Tester.  

z

For best results, use an automatic taper-rate battery charger with a voltage capability of 16 volts.  

z

The charging area should be well ventilated.  

z

Do not charge a battery that appears to be frozen. Allow the battery to warm to room temperature and test 
it using the J-42000 before charging.  

BATTERY STATE OF CHARGE 

The maintenance-free batteries SOC is estimated by reading the voltage of the battery across the battery 
terminals. Because the voltage is affected by current flow into or out of the battery, the engine must be stopped 
and all electrical loads turned OFF, including parasitic loads, when checking the voltage. The voltage can also 
be affected if the battery has just been charged or discharged, so it is important to consider what has happened 
to the battery in the time just before testing. Use the following procedure to determine the batteries SOC:  

1. Be sure all electrical loads are turned OFF.  

2. Determine whether the battery has been used in a vehicle or charged within the past 12 hours. 

z

If the answer is no, the terminal voltage will be stabilized and no action is necessary before reading 
the voltage. Skip to step 3 .  

z

If the answer is yes, terminal voltage will not be stabilized and you should wait 12 hours since the 
last time the battery was used.  

3. Estimate the battery temperature by determining the average temperature to which the battery has been 

exposed for the past 12 hours.  

4.  

NOTE:

Using voltage to determine the batteries state of charge (SOC) is only accurate 
after the battery has been at rest for 24 hours. This is enough time for the acid 
in each cell to equalize. If the battery has been charged or discharged in the 
past 24 hours, the battery SOC will only be an estimate. 

NOTE:

The table is accurate to 10 percent only after the battery has been at rest 

 

2004 Hummer H2 

2004 STARTING & CHARGING SYSTEMS Starters - H2