U0100 – Lost Communication with ECM/PCM: Causes, Symptoms & Fix

DTC U0100 means your car’s control modules cannot communicate with the ECM/PCM (Engine or Powertrain Control Module), which can cause no-start conditions or performance issues.

❓ What is Code U0100?

U0100 – Lost Communication with ECM/PCM
This fault occurs when a vehicle’s CAN (Controller Area Network) system detects no response from the ECM or PCM, which controls the engine, transmission, and major functions.

⚠️ Symptoms of U0100

• 🚫 No crank or no start

• ⚠️ Check engine light ON

• 🔌 Multiple system warning lights (ABS, ESC, airbag)

• 🚗 Limp mode or poor performance

• 🛠️ Communication errors during OBD scanning

🔍 Common Causes

1. 🔌 Disconnected or damaged ECM/PCM wiring

2. ⚡ Dead car battery or weak voltage

3. 🔧 Faulty ECM/PCM

4. 💥 Blown fuses or power relay failure

5. 🧠 CAN bus wiring short or open circuit

🛠️ How to Fix U0100

✅ 1. Inspect Battery & Fuses

Weak battery or blown fuses often disrupt ECM communication.
👉 Engine Components & Assemblies →

✅ 2. Check ECM/PCM Connectors

Look for corrosion, loose plugs, or water damage.

✅ 3. Scan Other Modules

Communication faults can cascade — check for other CAN bus errors.

✅ 4. Replace Faulty ECM/PCM if Required

👉 Shop ECU & Related Parts →

🛒 Relevant Parts on nayapurnaonline.com

• ⚙️ Engine & ECU Assemblies

• 🛠️ Brake & ABS Parts (for linked faults)

• 🚗 Tata Electrical & Engine Control Parts

• 🚘 Hyundai ECU & Control System Parts

• 🚙 Honda Engine & Electronics Parts

🚗 Commonly Affected Vehicles

💡 Quick Tips

• Always disconnect battery before checking ECM wiring

• Inspect for rodent-damaged wires in engine bay

• U0100 is serious — driving may be impossible if communication is lost

✅ Final Words

A U0100 code means your car’s brain (ECM/PCM) is out of communication. Fix it fast with quality-tested control modules and wiring components from nayapurnaonline.com.