Hydraulic Control Unit (HCU) Replacement

1. Raise and support vehicle, disconnect battery cables, then remove battery.
2. Remove battery tray attaching bolts, then tray.
3. Disconnect pump motor and fluid level sensor electrical connectors from HCU.

Fig 66 Controller Anti-Lock Brake System (CAB) Connector Locking Latch:

4. Ensure ignition switch is in the OFF position, then disconnect 37 way connector using a screwdriver. Lift connector latch away from connector, then rotate connector latch until fully against CAB. This will lift CAB connector away from CAB terminal.

Fig 67 Connector Removal From Controller Anti-Lock Brake System (CAB):

5. Grab connector and rotate rear of connector up until it clears connector pins on CAB. Remove CAB connector pin from latch on CAB and place off to side.
6. Disconnect the two brake tubes from proportioning valves, two brake fluid tubes from the master cylinder at HCU, two brake fluid output tubes from valve block on HCU, then brake fluid supply hose from master cylinder reservoir. Plug ends of supply hose so brake fluid will not drain out of master cylinder.
7. Remove HCU bracket to left inner fender attaching bolts, then two HCU bracket to left frame rail mounting bolts.
8. Remove HCU and mounting bracket from vehicle as an assembly.
9. Transfer CAB module from HCU to replacement HCU.
10. Reverse procedure to install noting the following:
a. Torque two bracket to frame rail attaching bolts to 14 ft. lbs.
b. Torque bracket to inner fender bolt to 18 inch lbs.
c. Prior to installing 37 way connector, ensure ignition switch is in the OFF position.
d. Bleed system as described under "Brake System Bleed."
e. Heat shield must be installed when replacing HCU. Failure to do so could result in failure to CAB do to high temperatures.