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ABS Warning Light

Audi Vehicle

Severity:

Source: OnlyErrorCodes.com — Every error code. One place.

Audi ABS Warning Light — What It Means & Fix

What Does This Error Mean?

Audi ABS warning light means the anti-lock braking system has detected a fault. Normal braking still works, but ABS is disabled. Use a VAG-compatible scanner (VCDS or OBDeleven) to read Audi-specific chassis fault codes — standard OBD-II tools often miss them.

Affected Models

  • Audi A3
  • Audi A4
  • Audi A5
  • Audi A6
  • Audi Q3
  • Audi Q5
  • Audi Q7
  • Audi TT
  • Audi Q8

Common Causes

  • Wheel speed sensor failed or wiring harness damaged — the most common cause across all Audi models
  • Tone ring cracked or corroded — the ring on the wheel bearing that the sensor reads
  • ABS/ESP hydraulic unit internal fault
  • ABS fuse blown
  • Low brake fluid level triggering multiple warnings simultaneously

How to Fix It

  1. Read ABS fault codes with a VAG-compatible scanner.

    Use VCDS (Ross-Tech), OBDeleven, or a scanner with full VW/Audi group support. Audi ABS codes are in the ABS/ESP control module (address 03). Common codes: 01130, 01131, 01132, 01133 (wheel speed sensors for each corner); C1020–C1030 series also appear on some models. The code identifies the exact wheel sensor that has failed.

  2. Inspect the wheel speed sensors and wiring.

    Audi wheel speed sensors are located at each wheel hub and route their wiring harness through the wheel arch. The most common failure on Audi A4 and A6 models is the wiring harness chafing against the wheel arch liner or suspension components — look for exposed bare wire in the harness. A sensor with a physically intact connector but a broken wire 10–20 cm back from the plug is a very common pattern.

  3. Check the wheel bearing and tone ring.

    Audi wheel bearings contain the ABS tone ring internally — a worn bearing can cause the ring to spin off-centre, producing erratic ABS sensor readings. Listen for a humming or grinding sound that changes with vehicle speed or when cornering. A faulty bearing typically needs replacing along with its integrated tone ring.

  4. Check the ABS fuse.

    Locate the ABS fuse in the main fuse box (usually in the engine bay or the passenger compartment fuse panel). Consult the Audi owner's manual or fuse box diagram for the ABS fuse location and rating. Replace a blown fuse with the same amperage — a repeatedly blowing fuse indicates a wiring fault in the ABS circuit.

  5. Have the ESP/ABS hydraulic unit tested.

    The Audi ABS and ESP systems share a combined hydraulic unit (Bosch unit on most models) that can develop internal faults — pump motor failure, pressure accumulator fault, or valve body issues. Multiple simultaneous sensor codes from different wheel positions often point to the hydraulic unit rather than individual sensors. A VAG specialist or Bosch-certified workshop can test the unit — rebuild or remanufactured replacement is often cheaper than a new dealer unit.

When to Call a Professional

Standard OBD-II scanners frequently fail to read Audi ABS fault codes. Use VCDS, OBDeleven, or a scan tool with VAG (Volkswagen Audi Group) support for an accurate diagnosis before replacing any parts.