ABS Pump

Remove and replace the ABS hydraulic control unit (pump/modulator assembly) including brake line disconnection, mounting hardware removal, and complete system bleeding.

Warnings

Tools required

Parts

• ABS hydraulic control unit (pump/modulator) × 1 — Use OEM Maserati specification
• Brake line crush washers × 6 — Use OEM specification

Fluids

• DOT 4 Racing Brake Fluid — 2 qt

Preparation

1. Park vehicle on level surface and engage parking brake
2. Disconnect negative battery terminal and wait 10 minutes for airbag system discharge
3. Raise front of vehicle and secure on jack stands rated for vehicle weight
4. Remove both front wheels
5. Place drain pan beneath ABS unit location (driver side of engine bay, near firewall)
6. Have all replacement parts and minimum 2 quarts of fresh DOT 4 Racing Brake Fluid ready
7. Ensure scan tool is connected and can communicate with ABS module before beginning

Procedure

1. 1

   Access ABS hydraulic control unit
   Locate the ABS pump assembly on the driver side of the engine bay near the firewall. Remove the plastic engine cover if equipped. Remove any interfering air intake ducting or wiring harness brackets that prevent clear access to the unit. The unit is a black metal assembly with multiple brake lines connected.
2. 2

   Disconnect electrical connectors
   Disconnect the main ABS pump electrical connector by pressing the release tab and pulling straight away from the unit. Note the connector orientation for reinstallation. If equipped, disconnect the brake fluid level sensor connector. Label all connections if necessary.
3. 3

   Mark and disconnect brake lines
   Using a permanent marker or tape, label each brake line connection point (typically 6 lines: 4 wheel circuits, 1 from master cylinder, 1 return). Using flare nut wrenches to prevent line damage, loosen each brake line fitting at the ABS unit. Have drain pan positioned below. Allow brake fluid to drain completely. Cap or plug each line immediately after removal to prevent contamination and further fluid loss.
   ⚠Use only flare nut wrenches on brake line fittings. Standard wrenches will round off the soft brass fittings.
   Torque spec

   Line Fittings22 Nm (16 lb-ft)
4. 4

   Remove ABS unit mounting hardware
   Locate the mounting bolts securing the ABS unit to its bracket (typically 2-3 bolts). Remove these bolts completely while supporting the weight of the unit. The assembly is heavy (approximately 10 lbs) and awkward to handle with brake lines still draining.
   Torque spec

   Mounting Bolts28 Nm (21 lb-ft)
5. 5

   Remove ABS hydraulic control unit
   Carefully lift the ABS unit out of the engine bay, maneuvering around any remaining obstructions. Keep the unit level to minimize additional fluid spillage. Place the old unit in a drain pan to catch residual brake fluid. Inspect the mounting bracket and surrounding area for corrosion or damage.
6. 6

   Prepare new ABS unit for installation
   Remove protective caps from all ports on the new ABS unit. Inspect each port for debris or damage. Compare the new unit to the old unit to verify correct part number and port configuration. Apply a small amount of fresh brake fluid to each port thread to aid installation and prevent cross-threading.
7. 7

   Install new ABS unit
   Position the new ABS unit onto the mounting bracket, aligning mounting holes. Install mounting bolts finger-tight first to ensure proper alignment. Torque mounting bolts to specification in a cross-pattern to ensure even seating.
   Torque spec

   Mounting Bolts28 Nm (21 lb-ft)
8. 8

   Reconnect brake lines
   Remove caps/plugs from brake lines. Install new crush washers on each brake line fitting. Thread each brake line into its marked port on the ABS unit by hand first to prevent cross-threading. Using flare nut wrenches, torque each line fitting to specification in the sequence: master cylinder line first, then wheel circuit lines, then return line last.
   ⚠Install brake lines carefully. Cross-threading will damage the ABS unit and require replacement.
   Torque spec

   Line Fittings22 Nm (16 lb-ft)
9. 9

   Reconnect electrical connections
   Reconnect the main ABS pump electrical connector, ensuring it clicks fully into place. Reconnect the brake fluid level sensor if previously disconnected. Verify all connections are secure and properly seated.
10. 10

    Reinstall wheels and lower vehicle
    Reinstall both front wheels. Torque lug nuts to specification in a star pattern. Lower vehicle from jack stands to ground. Do not remove jack stands yet as bleeding procedure may require access.
    Torque spec

    Wheel Lug Nuts140 Nm (103 lb-ft)
11. 11

    Fill brake fluid reservoir
    Locate the brake fluid reservoir under the hood. Fill to the MAX line with fresh DOT 4 Racing Brake Fluid. Keep the reservoir topped off throughout the bleeding process.
    ⚠️Never allow the brake fluid reservoir to run empty during bleeding or air will enter the system requiring restart of bleeding procedure.
12. 12

    Perform manual brake bleeding
    Starting with the wheel furthest from the master cylinder (typically right rear), attach bleeder hose to bleeder screw. Have assistant pump brake pedal 3-5 times and hold. Open bleeder screw, allow fluid and air to escape, close bleeder screw before pedal reaches floor. Repeat until fluid runs clear with no air bubbles. Proceed to left rear, right front, then left front. Check fluid level frequently.
    Torque spec

    Bleeder Screw10 Nm (7 lb-ft)
13. 13

    Perform ABS pump bleeding with scan tool
    Reconnect negative battery terminal. With scan tool connected, navigate to ABS system functions. Select 'ABS Pump Bleeding' or 'Hydraulic Unit Bleeding' function. Follow scan tool prompts to activate ABS pump motor and solenoid valves. This cycles internal valves to purge trapped air. During this process, continue manual bleeding at each wheel as directed by scan tool. This typically requires 2-3 complete cycles through all four wheels.
    ⚠ABS pump bleeding must be performed with scan tool. The internal valves cannot be opened manually and will trap air without electronic activation.
14. 14

    Verify brake system operation
    With engine running, pump brake pedal several times and verify firm pedal feel within 2-3 pumps. Pedal should not sink to floor under steady pressure. Check for any brake fluid leaks at all line connections and bleeder screws. Clear any ABS fault codes with scan tool. Verify ABS warning light extinguishes after engine start.

Reassembly

1. Reinstall any air intake ducting or engine covers removed during access
2. Clean any spilled brake fluid from engine bay and chassis components with water
3. Verify all tools and parts have been removed from engine bay
4. Top off brake fluid reservoir to MAX line after final verification

Verification

• Start engine and verify ABS warning light extinguishes within 3 seconds
• Perform test drive in safe area at low speed (under 15 mph) and verify normal brake operation
• Perform moderate braking and verify firm pedal with no pulsation or softness
• Perform ABS activation test on safe surface (wet pavement or gravel) to verify ABS engages properly
• Recheck all brake line fittings for leaks after test drive
• Use scan tool to verify no ABS fault codes are present
• Verify brake fluid level is at MAX line in reservoir

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