This procedure covers the removal and replacement of the ABS hydraulic control unit (HCU/pump) on a 2016-2024 Hyundai Tucson with the 2.5L I4 engine and AWD, including brake system bleeding and verification.

Warnings

Tools required

Parts

• ABS Hydraulic Control Unit (HCU) × 1 — Use OEM specification for 2.5L AWD model
• Brake line crush washers/seals × 1 — OEM brake line seal kit

Fluids

• DOT 4 Brake Fluid — 1 qt

Preparation

1. Park vehicle on level ground and apply parking brake
2. Place wheel chocks behind rear wheels
3. Open hood and locate battery in engine compartment
4. Disconnect negative battery terminal and wait minimum 3 minutes before proceeding
5. Locate ABS HCU assembly in engine compartment on driver side near brake master cylinder
6. Place drain pan or absorbent material under ABS unit work area to catch brake fluid
7. Top off brake fluid reservoir to MAX line with fresh DOT 4 fluid
8. Have at least 1 quart of fresh DOT 4 brake fluid ready for bleeding procedure

Procedure

1. 1

   Remove engine compartment covers and air intake components
   Remove the engine cover by pulling upward on the front clips. Remove the air intake duct and air filter housing if necessary to access the ABS unit. On the 2.5L AWD model, the ABS HCU is located on the driver side of the engine bay near the strut tower.
2. 2

   Disconnect ABS HCU electrical connectors
   Locate the main electrical connector on the ABS HCU. Press the locking tab and carefully disconnect the connector. If equipped with additional ground wires or secondary connectors, disconnect these as well. Mark connector orientation with tape if needed for reinstallation.
3. 3

   Identify and mark brake lines
   The ABS HCU has six brake line connections: two inlet lines from the master cylinder and four outlet lines to each wheel. Use masking tape or a marker to label each brake line connection (LF, RF, LR, RR, Inlet 1, Inlet 2) to ensure correct reconnection. Take a photo for reference.
4. 4

   Disconnect brake lines from ABS HCU
   Using the appropriate flare nut wrench (10mm or 12mm), carefully loosen each brake line connection at the ABS unit. Work slowly to avoid rounding the fittings. Have rags ready to catch fluid that will drain. Cap or plug each open line and port immediately with rubber caps or clean plastic wrap to prevent contamination and excessive fluid loss.
   ⚠Use only flare nut wrenches on brake line fittings. Standard wrenches will round the soft brass fittings and cause leaks.
5. 5

   Remove ABS HCU mounting hardware
   Locate the two or three mounting bolts securing the ABS HCU bracket to the body. These are typically 10mm or 12mm bolts. Remove all mounting hardware and carefully lift the ABS unit away from the mounting location. Be prepared for residual brake fluid to drain from the unit.
   Torque spec

   Mounting Bolts27 Nm (20 lb-ft)
6. 6

   Prepare new ABS HCU for installation
   Unpack the new ABS HCU and verify it matches the old unit exactly in connector configuration and brake line port locations. Install new crush washers/seals on all brake line fittings. Do not reuse old seals. Ensure all protective caps are removed from ports on the new unit before installation.
7. 7

   Install new ABS HCU
   Position the new ABS HCU into the mounting bracket location. Install mounting bolts finger-tight first to ensure proper alignment. Once aligned, torque mounting bolts to specification. Ensure the unit is securely mounted and does not move when gently pulled.
   Torque spec

   Mounting Bolts27 Nm (20 lb-ft)
8. 8

   Reconnect brake lines
   Thread each brake line fitting into the correct port on the new ABS HCU by hand first to prevent cross-threading. Reference your labels and photos from disassembly. Once all lines are hand-tight, use the flare nut wrench to snug each connection. Do not overtighten brake line fittings - typically 12-15 Nm is sufficient, though no specific torque is provided. Fittings should be snug but not forced.
   ⚠Cross-threading brake line fittings will ruin the new ABS unit. Always start fittings by hand and ensure they thread smoothly before using a wrench.
9. 9

   Reconnect electrical connections
   Reconnect the main ABS HCU electrical connector, ensuring it clicks firmly into place. Verify the locking tab is fully engaged. Reconnect any ground wires or secondary connectors removed earlier.
10. 10

    Reconnect battery and check for leaks
    Reconnect the negative battery terminal. Turn the ignition to ON position (do not start engine). Check all brake line connections at the ABS unit for any signs of fluid leakage. Wipe connections dry and observe for 1-2 minutes. If any leaks are detected, turn off ignition and tighten the affected fitting slightly.
11. 11

    Perform initial brake fluid fill
    Check brake fluid reservoir level and top off to MAX line with fresh DOT 4 fluid. Do not allow reservoir to drop below MIN line at any point during the bleeding process. Keep the fluid container nearby for frequent refilling.
12. 12

    Bleed brake system - manual bleeding phase
    Starting with the wheel farthest from the master cylinder (right rear), attach a clear hose to the bleeder screw and submerge the other end in a container of clean brake fluid. Have an assistant pump the brake pedal 5-6 times and hold. Open the bleeder screw, allow fluid to flow until stream is steady, then close before pedal reaches floor. Repeat until no air bubbles appear. Proceed to left rear, right front, then left front. Check and refill reservoir after each wheel.
    ⚠Never allow the brake pedal to reach the floor completely as this can damage the master cylinder. Close bleeder before pedal bottoms out.
    Torque spec

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

    Perform ABS modulator bleeding with scan tool
    Connect a professional scan tool with ABS bleeding function. Navigate to the Hyundai ABS bleeding procedure. The scan tool will cycle the ABS solenoid valves open to purge air from the modulator. Follow the scan tool prompts, which typically involve activating each corner in sequence. Monitor brake fluid reservoir constantly and refill as needed. After scan tool cycling is complete, repeat manual bleeding at all four wheels in the same sequence (RR, LR, RF, LF).
    ⚠️The scan tool ABS bleeding cycle is mandatory. Without this step, air will remain trapped in the ABS modulator and brakes will not function properly.
14. 14

    Final system check and test
    With engine off, pump brake pedal 10-15 times. Pedal should feel firm and not sink. If pedal is spongy, repeat bleeding procedure. Start engine and verify ABS warning light turns off after 2-3 seconds. Check all brake line connections one final time for leaks. Top off brake fluid reservoir to MAX line. Clean any spilled brake fluid from painted surfaces immediately.

Reassembly

1. Reinstall air intake components and engine covers removed during access
2. Verify all electrical connectors are fully seated and locked
3. Double-check brake fluid level is at MAX line
4. Ensure no tools or rags are left in engine compartment

Verification

• Start engine and verify ABS warning light illuminates briefly then turns off within 3 seconds
• With engine running, press brake pedal firmly - it should feel solid and not sink to the floor
• Perform a low-speed test drive in a safe area (under 10 mph) to verify brake function before normal driving
• Perform a controlled ABS activation test at low speed on a safe surface to verify ABS system functions correctly
• Recheck all brake line connections for leaks after test drive
• Check brake fluid level after test drive and top off if needed
• Use scan tool to verify no ABS fault codes are present in system memory

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