Removing and installing ABS control unit J104/ABS hydraulic unit N55, Audi S1 — AUDI

🧭 Before you start

Fits: Audi A1 (8X, 2010–2018)

• Opens: brake fluid

Don't miss

• This closes the valves in the brake master cylinder and stops the brake fluid reservoir from running empty.
• The brake pedal actuatorV.A.G 1869/2 must not be removed.
• Mark, disconnect and seal remaining brake lines leading to brake calipers.
• Make sure brake fluid does not get into connector housing of control unit. This can result in corrosion of the contacts and failure of the system.Use compressed air to carefully clean connector housing if necessary.
• To facilitate installation, moisten the rubber mountings slightly with water.

📋 Procedure

1. Remove air cleaner housing 24Air cleaner; Removing and installing air cleaner housing.
2. Take engine control unit J623 out of bracket 24Engine control unit; Removing and installing engine control unit J623 and tie up to one side.
3. Insert brake pedal actuatorV.A.G 1869/2 between brake pedal and driver's seat. Depress brake pedal by at least 60 mm. [Note: This closes the valves in the brake master cylinder and stops the brake fluid reservoir from running empty.]
4. ⚠ Risk to healthBrake fluid is poisonous and must NOT be drawn off by sucking through a hose.Always wear chemical-resistant protective gloves to prevent brake fluid from contacting skin.Always observe the relevant environmental regulations for disposal.Risk of malfunction if brake fluid comes into contact with fluids containing mineral oils.Do not under any circumstances allow brake fluid to come into contact with fluids that contain mineral oils (e.g. oil, petrol, cleaning agents). Protective gloves must be free of oil and grease.Risk of damage to paintwork surfacesDue to its corrosive effect, brake fluid must not be allowed to come into contact with paintwork. Rinse off brake fluid spillages immediately using plenty of water. — Detach protective cap on bleeder screw of front left brake caliper.
5. Fit bleeder hose (1) of reservoir onto bleeder screw.

6. Open bleeder screw to relieve pressure in hydraulic system.
7. Repeat this procedure at rear left brake.
8. Close bleeder screws (front left and rear left). [Note: The brake pedal actuatorV.A.G 1869/2 must not be removed.]
9. Place sufficient lint-free cloths (arrow) under control unit and hydraulic unit.
10. Unscrew union screws (arrows) and detach brake lines (1, 2).
11. Mark, disconnect and seal remaining brake lines leading to brake calipers.
12. Unscrew unions (arrows), lift brake lines clear and tie up.
13. Seal open connections immediately using clean sealing plugs from repair kit1H0 698 311 A.
14. ⚠ Risk of damage to brake linesDo not attempt to bend to a different shape. — Unplug electrical connector (1) on ABS control unit J104(item 2). [Note: Make sure brake fluid does not get into connector housing of control unit. This can result in corrosion of the contacts and failure of the system.Use compressed air to carefully clean connector housing if necessary.]
15. Loosen nuts (arrows) and lift hydraulic unit with control unit (1) off bracket (pay attention to brake lines).
16. ⚠ Risk of irreparable damage to hydraulic control unitTake care to protect the control unit from knocks and impact; if dropped, the hydraulic control unit can no longer be used. — Place hydraulic control unit base down on a clean flat surface. [Note: Do not remove the sealing plugs from the new hydraulic control unit until you are ready to fit the corresponding brake line.If the sealing plugs are removed from the hydraulic control unit too soon, brake fluid may escape and it may not be possible to fill and bleed the unit properly.]
17. Fit hydraulic control unit in bracket and tighten nuts (arrows). [Note: To facilitate installation, moisten the rubber mountings slightly with water.]
18. Remove sealing plugs from new hydraulic control unit. [Note: For easier installation, first insert all the brake lines in the hydraulic control unit and then tighten the brake line connections.]
19. Insert all brake lines and tighten connections.
20. ⚠ Risk of ABS/ESP malfunctionsMark brake line connections; do not interchange. — Perform final control diagnosis after securing brake lines to hydraulic control unit . [Note: Final control diagnosis can be used to establish whether line connections have been interchanged.]
21. Install engine control unit J62324Engine control unit; Removing and installing engine control unit J623.
22. Install air cleaner housing 24Air cleaner; Removing and installing air cleaner housing.
23. Bleed brake system .
24. When renewing ABS control unit J104/ABS hydraulic unit N55, select the "“Replace”" function for the ABS control unit J104/ABS hydraulic unit N55 using , Guided Functions.

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