With VCM/Four Wheel Antilock Brake System

VCM/FOUR WHEEL ANTILOCK BRAKE SYSTEM BLEEDING
The brake pressure modulator valve (BPMV) should be bled after replacement or if air is trapped in it. Bleeding should not be necessary if the fluid is not contaminated or no air is in the BPMV. There are internal bleed valves on each side of the BPMV that open internal channels. Open the internal bleed valves 1/4 to 1/2 turn before bleeding. Should the module need bleeding, it must be bled after the master cylinder and before the wheel cylinders and calipers.

NOTICE: The ignition switch must be in the "OFF" position or false trouble codes could be set to memory.

Tools Required:
- J 39177 Combination Valve Pressure Bleeding Tool (Three required)
- TK 00000 Tech-1 Scan Tool
- TK 02650 RWAL/4WAL Cartridge Kit or 3000003 Mass Storage Cartridge
- A modified J 35856 Combination Valve Pressure Bleeding Tool can be used in place of J 39177 providing you remove the dimple from it first.

Important: Expect to use two quarts of brake fluid to thoroughly bleed the system.

Fig. 59 EHCU/BPMV Module Bleeding:

1. Open the internal bleed valves on the sides of the BPMV 1/4 to 1/2 turn each (A).
2. Install J 39177 on the left high pressure accumulator bleed stem (C) of the BPMV.
3. Install J 39177 on the right high pressure accumulator bleed stem (C) of the BPMV.

Combination Valve Pressure Bleeding Tool:

4. Install J 39177 on the combination valve.
5. Check the master cylinder reservoir fluid level and fill if needed.
6. Bleed the brakes as described under Pressure Bleeding.

NOTICE: Always use the correct fastener in the proper location. When you replace a fastener, use ONLY the exact part number for that application. General Motors will call out those fasteners that require a replacement after removal. General Motors will also call out the fasteners that require thread lockers or thread sealant. UNLESS OTHERWISE SPECIFIED, do not use supplemental coatings (paints, greases, or other corrosion inhibitors) on threaded fasteners or fastener joint interfaces. Generally, such coatings adversely affect the fastener torque and the joint clamping force, and may damage the fastener. When you install fasteners, use the correct tightening sequence and specifications. Following these instructions can help you avoid damage to parts and systems.

7. Close the internal bleed valves. Tighten Internal bleed valves (A) to 7 Nm (60 lbs. in.).
8. Remove the three J 39177 tools.
9. Check the master cylinder reservoir fluid level and fill if needed.
10. With the ignition switch "ON" and the engine off, do six function tests with the Tech-1 scan tool.
11. Repeat the wheel cylinder and caliper bleed procedure to remove the air that purged from the BPMV during the tunction tests.
12. Apply firm pressure to the brake pedal and evaluate brake pedal feel.
13. Repeat the bleed procedure if needed.
- Make sure you have a good, hard brake pedal before starting the engine and moving the vehicle.