Hummer H2. Manual - part 787

14. Repair or replace any brake caliper that was not operating properly. Refer to the appropriate procedure. 

Perform brake caliper overhaul. See BRAKE CALIPER under OVERHAUL. If the repair and/or 
replacement was completed, go to step 21 .  

15. Bleed the hydraulic brake system to observe for the presence of air in the system and to observe for an 

unrestricted and even flow of brake fluid per axle during the bleeding procedure. See BLEEDING 
BRAKE SYSTEM . If there was air in the system, go to step 19 . If there was no air in the system, go to 
step 16 .  

16. If the flow of brake fluid was unrestricted and even per axle during the bleeding procedure, go to step 21 . 

If the flow of brake fluid was not unrestricted and even per axle during the bleeding procedure, go to step 
17 .  

17.

A. Inspect the hydraulic brake pipes and flexible brake hoses for signs of a fluid restriction; such as 

being bent, kinked, pinched or damaged. See BRAKE PIPE & HOSE INSPECTION under 
ADJUSTMENTS & INSPECTION.  

B. Replace any of the hydraulic brake pipes and/or flexible brake hoses found to be bent, kinked, 

pinched, or damaged. Refer to the following procedures as necessary: 

z

Replace brake hose. See BRAKE HOSE under REMOVAL & INSTALLATION.  

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Replace brake pipe. See BRAKE PIPE under REMOVAL & INSTALLATION.  

C. If none of the hydraulic brake pipes or flexible brake hoses were visibly bent, kinked, pinched, or 

damaged, replace the hydraulic brake flex hose at the restricted location.  

If the condition was found and corrected, go to step 21 . If the condition was not found and corrected, go 
to step 18 .  

18. Replace the brake pressure modulator valve (BPMV), in order to correct the hydraulic brake dynamic rear 

proportioning mechanical operation. See BRAKE PRESSURE MODULATOR VALVE in appropriate 
ANTI-LOCK article in BRAKES. After repairs are complete, go to step 21 .  

19.

A. Inspect the hydraulic brake system components for brake fluid seepage at a seal and/or fitting 

location, which may have drawn air into the system.  

B. Inspect the hydraulic brake system components for evidence of a recent repair, which may have 

introduced air into the system.  

C. Repair or replace any of the components found to be installed incorrectly or seeping brake fluid.  

If the condition was found and corrected, go to step 21 . If the condition was not found and corrected, go 
to step 20 .  

20.

A. Inspect the brake master cylinder for internal fluid leaks. See BRAKE SYSTEM INTERNAL 

LEAK TEST under SYSTEM TESTS.  

B. Repair or replace the brake master cylinder if it is found to be leaking brake fluid internally. See 

MASTER CYLINDER under OVERHAUL and/or MASTER CYLINDER under REMOVAL & 
INSTALLATION.  

If the condition was found and corrected, go to step 21 . If the condition was not found and corrected, 
return to symptom test.  

21. Install or connect components that were removed or disconnected during diagnosis. If the operation was 

 

2004 Hummer H2 

2003-04 BRAKES Disc - Hummer

  

completed, hydraulic brake system okay. If the operation was not completed, return to symptom tests.  

PARK BRAKE SYSTEM DIAGNOSIS 

1. If you were sent here from a hydraulic brake symptom test, go to step 4 . If you were not sent here from a 

hydraulic brake symptom test, go to step 2 .  

2. If you were sent here from a park brake symptom test, go to step 4 . If you were sent here from a park 

brake symptom test, go to step 3 .  

3. If the symptom is related to the ability of the park brake system to hold and/or release, see PARK 

BRAKE SYSTEM under GENERAL DIAGNOSIS. If the symptom is not related to the ability of the 
park brake system to hold and/or release, see HYDRAULIC BRAKE SYSTEM under GENERAL 
DIAGNOSIS.  

4.

A. Raise and support the vehicle with the rear axle supported by jack stands.  

B. Shift the transmission into neutral.  

C. With the park brake released, attempt to rotate the rear wheels to check the rear brakes for a 

significant amount of drag.  

If the rear brakes have a significant amount of drag, go to step 11 . If the rear brakes DO NOT have a 
significant amount of drag, go to step 5 .  

5.

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Shift the transmission into neutral.  

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Apply the park brake.  

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Attempt to rotate the rear wheels to check the rear brakes for a significant amount of drag.  

If the rear brakes have a significant amount of drag, go to step 6 . If the rear brakes DO NOT have a 
significant amount of drag, go to step 7 .  

6. Release the park brake. Rotate the rear wheels to check the rear brakes for a significant reduction in the 

amount of drag. If the rear brakes exhibit a significant reduction in the amount of drag, go to step 22 . If 
the rear brakes DO NOT exhibit a significant reduction in the amount of drag, go to step 11 .  

7. Visually check the park brake cable connections and the cables that are accessible on the underside of the 

vehicle for disconnections and/or damage. If any or the park brake cables were disconnected and/or 
damaged, go to step 8 . If any or the park brake cables were not disconnected and/or damaged, go to step 
9 .  

8. Reconnect or replace the park brake cables as necessary. See PARK BRAKE CABLE under 

REMOVAL & INSTALLATION. If the repair and/or replacement was completed, go to step 9 .  

9. Check the adjustment of the park brake. See PARK BRAKE ADJUSTMENT under ADJUSTMENTS 

& INSPECTION. If the park brake was adjusted properly, go to step 11 . If the park brake was not 
adjusted properly, go to step 10 .  

10. Adjust the park brake. See PARK BRAKE ADJUSTMENT under ADJUSTMENTS & INSPECTION. 

If the adjustment of the park brake was attainable, go to step 16 . If the adjustment of the park brake was 
not attainable, go to step 11 .  

11.  

 

2004 Hummer H2 

2003-04 BRAKES Disc - Hummer

  

Remove the rear brake rotors. See BRAKE ROTOR in REMOVAL & INSTALLATION. Inspect the 
park brake shoe hardware for looseness, damaged, broken or missing components. Check the park brake 
actuators for a seized condition. If the park brake hardware and/or the park brake actuators require 
replacement, go to step 12 . If the park brake hardware and/or the park brake actuators DO NOT require 
replacement, go to step 13 .  

12. Replace park brake hardware components as necessary. See PARK BRAKE SHOES under REMOVAL 

& INSTALLATION. Replace the park brake actuators as necessary. See PARK BRAKE ACTUATOR 
under REMOVAL & INSTALLATION. After repairs are complete, go to step 13 .  

13. Have an assistant apply and release the park brake, while you observe the park brake cables for free 

movement. If the park brake cables moved freely, go to step 14 . If the park brake cables did not move 
freely, go to step 17 .  

14. Check the adjustment of the park brake. See PARK BRAKE ADJUSTMENT under ADJUSTMENTS 

& INSPECTION. If the park brake was adjusted properly, go to step 16 . If the park brake was not 
adjusted properly, go to step 15 .  

15. Adjust the park brake. See PARK BRAKE ADJUSTMENT under ADJUSTMENTS & INSPECTION. 

If the adjustment of the park brake was attainable, go to step 16 . If the adjustment of the park brake was 
not attainable, go to step 25 .  

16. With the transmission still in neutral, apply the park brake. Attempt to rotate the rear wheels to check the 

rear brakes for a significant amount of drag. Release the park brake. Rotate the rear wheels to check the 
rear brakes for a significant reduction of drag. If the park brake applied and released properly, go to step 
27 . If the park brake did not apply and release properly, return to symptom tests.  

17. Disconnect the park brake cable connections that are accessible on the underside of the vehicle one at a 

time and check each cable for free movement. If any of the park brake cables that are accessible on the 
underside of the vehicle require replacement, go to step 18 . If any of the park brake cables that are 
accessible on the underside of the vehicle DO NOT require replacement, go to step 19 .  

18. Replace any of the park brake cables that DO NOT have free movement and/or are not releasing properly. 

See PARK BRAKE CABLE under REMOVAL & INSTALLATION. After repairs are complete, go to 
step 19 .  

19. Disconnect the front park brake cable connection accessible INSIDE the vehicle at the park brake pedal 

assembly and check for free movement. Replace the front park brake cable if it does not have free 
movement. See PARK BRAKE CABLE under REMOVAL & INSTALLATION. If the condition was 
found and corrected, go to step 25 . If the condition was not found and corrected, go to step 20 .  

20. Disconnect the park brake release handle assembly cable connection from the park brake pedal assembly 

and check for free movement. Replace the park brake release handle assembly if the release cable does 
not have free movement. See PARK BRAKE RELEASE HANDLE ASSEMBLY under REMOVAL & 
INSTALLATION. If the condition was found and corrected, go to step 25 . If the condition was not found 
and corrected, go to step 21 .  

21. Replace the park brake pedal assembly that is not releasing properly. See PARK BRAKE PEDAL 

ASSEMBLY under REMOVAL & INSTALLATION. After repairs are complete, go to step 25 .  

22. Check the adjustment of the park brake. See PARK BRAKE ADJUSTMENT under ADJUSTMENTS 

NOTE:

DO NOT depress the brake pedal with the brake rotors and/or the brake 
drums removed or with the brake calipers repositioned away from the 
brake rotors. Damage to the brake system may result. 

 

2004 Hummer H2 

2003-04 BRAKES Disc - Hummer

  

& INSPECTION. If the park brake was adjusted properly, go to step 27 . If the park brake was adjusted 
properly, go to step 23 .  

23. Adjust the park brake. See PARK BRAKE ADJUSTMENT under ADJUSTMENTS & INSPECTION. 

If the adjustment of the park brake system attainable, go to step 26 . If the adjustment of the park brake 
system is not attainable, go to step 24 .  

24.

A. Remove the rear brake rotors, if they have not yet been removed. See BRAKE ROTOR in 

REMOVAL & INSTALLATION.  

B. Check the park brake actuators for a seized condition.  

C. Replace the park brake actuators as necessary. See PARK BRAKE ACTUATOR under 

REMOVAL & INSTALLATION.  

If the condition was found and corrected, go to step 25 . If the condition was not found and corrected, 
return to symptom test.  

25. Adjust the park brake. See PARK BRAKE ADJUSTMENT under ADJUSTMENTS & INSPECTION. 

If the adjustment of the park brake system was attainable, go to step 26 . If the adjustment of the park 
brake system was not attainable, return to symptom test.  

26. With the transmission still in NEUTRAL, apply the park brake. Attempt to rotate the rear wheels to check 

the rear brakes for a significant amount of drag. Release the park brake. Rotate the rear wheels to check 
the rear brakes for a significant reduction of drag. If the park brake applied and released properly, go to 
step 27 . If the park brake did not apply and release properly, return to symptom test.  

27. Install or connect any components that were removed or disconnected during diagnosis. If the operation 

was completed, park brake system okay. If the operation was not completed, return to symptom table.  

SYMPTOM TESTS 

BRAKE WARNING INDICATOR ALWAYS ON 

1. If the hydraulic brakes operation has been reviewed and the necessary inspection performed, go to step 2 . 

If the hydraulic brakes operation has not been reviewed and the necessary inspection has not been 
performed, see HYDRAULIC BRAKE SYSTEM under GENERAL DIAGNOSIS in TROUBLE 
SHOOTING.  

2. Inspect the brake fluid level. If the brake fluid level is okay, go to step 3 . If the brake fluid level is not 

okay, see BRAKE FLUID LOSS .  

3.

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

B. Disengage the park brake.  

C. With a scan tool, observe the park brake switch parameter in the BCM Inputs data list.  

If the scan tool indicates that the park brake switch parameter is inactive, go to step 4 . If the scan tool 
does not indicate that the park brake switch parameter is inactive, go to step 5 .  

4. With a scan tool, observe the brake warning light parameter in the Instrument Panel Cluster (IPC) inputs 

data list. If the scan tool indicates that the brake warning light parameter is on, go to step 12 . If the scan 
tool does not indicate that the brake warning light parameter is on, go to step 6 .  

 

2004 Hummer H2 

2003-04 BRAKES Disc - Hummer