Hummer H2. Manual — part 776

J 39700-530

Cable Adapter

2004 Hummer H2

2004 BRAKES Anti-Lock Brake System - Hummer H2

Tech 2

Scan Tool

2004 Hummer H2

2004 BRAKES Anti-Lock Brake System - Hummer H2

2003-04 BRAKES

Disc - Hummer

MODEL IDENTIFICATION

Vehicle model can be identified by fifth character of Vehicle Identification Number (VIN), stamped on metal
pad on top of left end of instrument panel, near windshield.

DESCRIPTION & OPERATION

HYDRAULIC BRAKE SYSTEM DESCRIPTION

Hydraulic Brake Master Cylinder Fluid Reservoir

Contains supply of brake fluid for the hydraulic brake system.

Hydraulic Brake Master Cylinder

Converts mechanical input force into hydraulic output pressure. Hydraulic output pressure is distributed from
the master cylinder through 2 hydraulic circuits, supplying front-rear opposed wheel apply circuits.

Hydraulic Brake Pressure Balance Control System

Regulates brake fluid pressure delivered to hydraulic brake wheel circuits, in order to control the distribution of
braking force. Pressure balance control is achieved through Dynamic Rear Proportioning (DRP), which is a
function of the ABS modulator. To identify DRP description, see DYNAMIC REAR PROPORTIONING under
DESCRIPTION & OPERATION in appropriate ANTI-LOCK article.

Hydraulic Brake Pipes and Flexible Brake Hoses

Carries brake fluid to and from hydraulic brake system components.

Hydraulic Brake Wheel Apply Components

Converts hydraulic input pressure into mechanical output force.

HYDRAULIC BRAKE SYSTEM OPERATION

Mechanical force is converted into hydraulic pressure by the master cylinder, regulated to meet braking system
demands by the pressure balance control system, and delivered to the hydraulic brake wheel circuits by the
pipes and flexible hoses. The wheel apply components then convert the hydraulic pressure back into mechanical
force which presses linings against rotating brake system components.

NOTE:

This article covers base brake systems only. For information on Anti-Lock
Brake System (ABS), see appropriate ANTI-LOCK article.

2004 Hummer H2

2003-04 BRAKES Disc - Hummer

2004 Hummer H2

2003-04 BRAKES Disc - Hummer

BRAKE WARNING SYSTEM

The Instrument Panel Cluster (IPC) illuminates the brake warning indicator when one or more of the following
occurs:

z

The Electronic Brake Control Module (EBCM) detects a low brake fluid condition. The IPC receives a
class 2 message from the EBCM requesting illumination.

z

The IPC detects the park brake is engaged. The IPC receives a Class 2 input from the Body Control
Module (BCM) requesting illumination.

z

The IPC performs the displays test at the start of each ignition cycle. The indicator illuminates for
approximately 3 seconds.

BRAKE HYDRAULIC ASSIST SYSTEM ASSIST DESCRIPTION

Brake Pedal

Receives, multiplies and transfers brake system input force from driver.

Brake Pedal Pushrod

Transfers multiplied input force received from brake pedal to brake booster.

Hydraulic Brake Booster

Uses power steering fluid pressure to decrease effort required by driver when applying brake system input
force. When brake system input force is applied, pressurized power steering fluid is admitted to the rear of an
apply piston, providing a decrease in brake pedal effort required. When input force is removed, pressurized
power steering fluid is blocked off from the piston.

Power Steering System

Supplies pressurized power steering fluid used by hydraulic brake booster to decrease brake pedal effort.

BRAKE ASSIST SYSTEM - HYDRAULIC ASSIST OPERATION

Brake system input force is multiplied by the brake pedal and transferred by the pedal pushrod to the hydraulic
brake master cylinder. Effort required to apply the brake system is reduced by the hydraulic brake booster.

DISC BRAKE SYSTEM DESCRIPTION

Disc Brake Pads

Applies mechanical output force from the hydraulic brake calipers to friction surfaces of brake rotors.

Disc Brake Rotors

Uses mechanical output force applied to friction surfaces from the disc brake pads to slow speed of tire and

2004 Hummer H2

2003-04 BRAKES Disc - Hummer