ABS module can only be bled using a scan tool capable of ABS system.
BLEEDING HYDRAULIC CONTROL UNIT (HCU)
1. Bleed base brake system using manual or pressure bleeding procedure.
2. Connect scan tool to Blue 16-pin Data Link Connector (DLC) located under lower dash panel,
to right of steering column.
3. Using scan tool, check for stored Diagnostic Trouble Codes (DTCs). See RETRIEVING
DIAGNOSTIC TROUBLE CODES under SELF-DIAGNOSTIC SYSTEM. If no DTCs exist, go to next step. If DTCs exist, clear DTCs from CAB using scan tool. Go to next step.
4. Go to BLEED ABS on scan tool and follow screen prompts to bleed brake system. Disconnect
scan tool. Repeat manual or pressure bleeding procedure on brake system.
You may also want to check your inline proportioning valves.
COMPONENT TESTING: PROPORTIONING VALVE
All Models RR, LR, RF, LF
WARNING: Ensure manual bleeding or pressure bleeding procedure is performed before bleeding Hydraulic Control Unit (HCU).
1. Road test vehicle to determine which rear wheel indicates a premature wheel skid. Remove
appropriate proportioning valve from brakeline. Proportioning valve is located on brakeline,
near flexible brakeline at frame rail.
2. Perform STEP 1. Remove mounting bracket from frame rail and brakeline clamps so brakelines will not be bent. Perform STEP 2. Install Adapters (6892) on each end of proportioning valve and install adapters and proportioning valve back on brakelines.
3. Install Pressure Gauge (C-4007-A) into each adapter. Bleed air from pressure gauges. Have an
assistant hold brake pedal down until pressure on inlet side of proportioning valve is 1000 psi
(70 kg/cm2 ) and note pressure on outlet side of proportioning valve. Pressure on outlet side
should be 600-700 psi (42-49 kg/cm2 ). Replace proportioning valve if pressure on outlet side
is not within specification.
4. Remove test equipment. Reinstall brakelines on proportioning valve. Tighten brakeline nuts.
Once brake system is bleed, perform pressure test on remaining proportioning