U0121 – Lost Communication with ABS Control Module: Symptoms, Causes & Fix

DTC U0121 means your car's systems cannot communicate with the ABS Control Module, often disabling anti-lock brakes and other safety features.

❓ What is Code U0121?

U0121 – Lost Communication with ABS Control Module
This code occurs when the CAN Bus detects no response from the ABS module, which manages anti-lock braking and stability control systems.

⚠️ Symptoms of U0121

• 🚨 ABS warning light ON

• ⚠️ ESC/Traction control disabled

• 🛑 Brake performance reduced

• 🔧 No communication with ABS module during scanning

• ❌ ABS won't function during hard braking

🔍 Common Causes

1. 💥 Faulty ABS Control Module

2. 🔌 Damaged ABS wiring or connectors

3. ⚡ CAN Bus short or open circuit

4. 🪫 Low battery or voltage irregularity

5. 💡 Aftermarket installations interfering with ABS wiring

🛠️ How to Fix U0121

✅ 1. Inspect ABS Wiring & Connectors

Look for corrosion, water ingress, or damage.
👉 Shop ABS & Brake Control Parts →

✅ 2. Check Battery Voltage

A weak battery can disrupt ABS communication.

✅ 3. Scan for Other CAN Bus Faults

Multiple communication errors may reveal wiring issues.

✅ 4. Replace Faulty ABS Control Module

👉 Engine & ECU Assemblies →

🛒 Relevant Parts on nayapurnaonline.com

• 🛡️ Brake & ABS Control Parts

• ⚙️ Engine & ECU Assemblies

• 🚗 Tata ABS & Electronic Spares

• 🚘 Hyundai ABS & Brake System Parts

• 🚙 Honda ABS Control & Sensors

🚗 Commonly Affected Vehicles

💡 Quick Tips

• Never pressure wash near the ABS unit

• Regularly inspect wiring for rodents or corrosion

• U0121 is a safety-critical fault — driving may be risky

✅ Final Words

A U0121 code disables your ABS and stability systems. Fix it quickly with quality-tested ABS modules, wiring, and ECU parts from nayapurnaonline.com.