Curing the C123EF0 ABS Fault Code

If you’re diagnosing a C123EF0 fault in an Audi or VW, chances are you’ve already seen ABS or ESP warning lights, logged the fault code, and found the ABS pump to be the issue. You’re not alone—it’s a frequent failure in the VAG range, and there’s a repeatable fix.

This page walks you through what the code means, what actually causes it, and how we repair the ABS pump quickly and properly at ECU Fix.

---

🔍 What Does the C123EF0 Code Actually Mean?

C123EF0: Hydraulic Brake Booster – Limit Value Reached.

It sounds like a pump issue—and it is—but the root cause often lies elsewhere.

This code usually indicates that the brake booster pressure sensor on the vehicle has started failing. It sends incorrect data to the ABS/ESP system. In response, the ABS pump over-activates and eventually sustains internal damage.

That’s why this fault usually always requires both ABS pump repair and sensor replacement.

---

🧰 Symptoms You’ll Typically See

Vehicles with this fault may show:

• ABS or ESP warning lights on the dash
• Brake pedal feel changing—usually firmer, with less assist
• Delayed braking or uneven pressure
• C123EF0 fault code during scan
• MOT brake test failure due to warning lights or reduced braking power

It’s also worth noting: clearing the code alone won’t solve the issue, and replacing the ABS pump without fixing the pressure sensor will almost always result in a repeat failure.

---

⚠️ Sensor Replacement Is Essential

We can reliably repair the ABS pump, but the repair will only hold if the faulty brake booster pressure sensor is replaced before the unit is refitted.

If not, the vehicle continues to feed incorrect data to the ABS system—and the newly repaired pump will fail again.

---

🛠 How We Fix the ABS Pump

At ECU Fix, we provide a fast and proven repair service for ABS pumps affected by C123EF0. We don’t just mask the issue—we fix the internal fault caused by prolonged stress or overload from the failing sensor.

Our process:

1. You book the service using the “Shop Now” option
   – This places your repair order directly through our site
2. We arrange UK-wide courier collection or accept posted units
   – You’ll receive packaging/shipping instructions after checkout
3. We test the ABS pump under simulated load conditions
   – If it’s listed in our catalogue, we test within 24 hours
4. We complete internal repairs
   – This includes motor rebuilds, circuit board rework, and hydraulic valve correction as needed
5. We return the repaired unit with a lifetime warranty
   – It’s plug-and-play with no coding required

---

🚗 Common Vehicles and Part Numbers – Examples Include, But Are Not Limited To

0265956241 / 0265956658 / 0265956840 / 0265956194 / 0265956226 / 0265956659

8W0907379J / 8W0907379Q / 8W0907379AF / 8W0614517N / 8W0614517H / 4M0907379K / 4G0907379T / 80A907379E / 8W0907379AA

---

⚙️ Why Use ECU Fix?

• We’re a dedicated ECU and module repair specialist, not a general electronics firm
• We fix the actual internal faults—not just clear codes or patch over the issue
• Every ABS unit is bench-tested under real-world conditions using professional equipment
• We offer a 24-hour testing guarantee on catalogue-listed pumps
• You get a lifetime warranty on every successful repair
• The process is simple—just click “Shop Now” on this page to book and send us the unit

---

🧾 How to Get Started

1. Click “Shop Now” to order the ABS pump repair service
2. Choose courier collection or send your unit to us directly
3. Make sure to replace the brake booster pressure sensor on the vehicle
4. Refit the repaired ABS pump— plug-and-play
5. Clear any fault codes, road test the vehicle, and hand it back with confidence

---

FAQs

What is the code C123EF0 on Audi?

The fault code C123EF0 on an Audi means “Hydraulic Brake Booster – Limit Value Reached.” It usually indicates that the brake booster pressure sensor is sending incorrect readings to the ABS/ESP system. Over time, this overstresses the ABS pump, causing internal damage. The fault commonly leads to ABS/ESP warning lights and reduced braking assistance.

---

What does “Brake Servo Restricted” mean on Audi?

The message “Brake Servo Restricted” signals a problem in the brake booster system, often due to insufficient pressure or incorrect readings from the brake pressure sensor. It can be linked to fault code C123EF0 and may result in a hard brake pedal, poor brake assist, and ABS or ESP faults.