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Brake Pressure Modulator Valve

NOTE: It is not necessary to bleed BPMV during normal brake system bleeding. If BPMV is replaced or is suspected to have air in it, BPMV must be bled. Expect to use 2-3 quarts of fluid to thoroughly bleed system. Bleeding BPMV requires Tech 1 and appropriate cartridge.
  1. Bleed BPMV after master cylinder, but before wheel cylinders/calipers. Ensure ignition is off. Install one combination valve depressor on combination valve. Install 2 Combination Valve Depressors (J-39177) on BPMV high pressure accumulator bleed stems. Rotate 2 BPMV internal bleed valves 1/4-1/2 turn counterclockwise. See Fig 1.
  2. Bleed wheel cylinders/calipers, using manual or pressure bleeding procedure. See the BRAKE SYSTEM article. Close BPMV internal bleed valves. Remove combination valve depressors from BPMV high pressure accumulator bleed stems. Remove combination valve depressors from combination valve.
    CAUTION: If internal bleed screws are left open, hydraulic fluid will by-pass accumulator, and hydraulic pressure will be lost.
  3. Connect Tech 1 scan tester with RWAL/4WAL cartridge or Mass Storage Cartridge to Data Link Connector (DLC). Ensure master cylinder fluid reservoir is full. Using Tech 1, perform 6 functional tests. All air should be removed from BPMV.
  4. Rebleed wheel cylinders/calipers. This will remove any air in brakelines from purging BPMV. Evaluate brake pedal feel and braking performance. Repeat bleeding procedure if necessary.
Fig 1: Locating BPMV Internal Bleed Valves
G92D22122Courtesy of GENERAL MOTORS CORP.