What is Liebherr General Fault Code E518?

Fault Code E518 indicates a malfunction in the Engine Coolant Temperature (ECT) Sensor Circuit, specifically detecting an implausible or out-of-range signal from the coolant temperature monitoring system. This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) receives voltage readings from the ECT sensor that fall outside the manufacturer's predetermined parameters, typically indicating either an open circuit, short circuit, or sensor degradation.

In Liebherr excavators, the ECT sensor plays a critical role in engine management by providing real-time coolant temperature data to the ECM. This information directly influences fuel injection timing, idle speed control, and engine protection protocols. When E518 activates, the ECM may default to failsafe mode, potentially limiting machine performance to prevent catastrophic engine damage from overheating or improper combustion.

Common Symptoms

• Engine warning lamp illuminated on the operator display with reduced engine power or derate mode activated
• Cooling fan running continuously at maximum speed regardless of actual engine temperature
• Difficulty starting the engine, particularly in cold weather conditions, due to improper fuel enrichment
• Erratic temperature gauge readings or temperature display showing unrealistic values (extremely high or low)
• Engine running rough during warm-up phase with excessive black smoke from the exhaust

Potential Causes

The most frequent causes of E518 in used Liebherr excavators include:

• ECT sensor internal failure due to age-related degradation or thermal cycling stress common in machines with 5,000+ operating hours
• Wiring harness damage at known rub points near the engine block or cylinder head where vibration causes insulation wear
• Corroded or loose connector terminals at the sensor plug, particularly in machines exposed to moisture or stored outdoors
• Coolant contamination causing sensor element coating or failure due to improper coolant mixture or lack of maintenance
• ECM internal fault (less common) affecting the temperature monitoring circuit or reference voltage supply

How to Troubleshoot and Fix Code E518

Step 1: Visual Inspection Begin by locating the ECT sensor (typically installed in the engine coolant passage near the thermostat housing). Inspect the wiring harness for visible damage, abrasion, or oil contamination. Check the connector for corrosion, bent pins, or moisture intrusion—common issues in used excavators operating in harsh environments.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure its resistance. At 68°F (20°C), resistance should typically read between 2,000-3,000 ohms (consult Liebherr specifications). Test the harness continuity from the sensor connector back to the ECM and check for shorts to ground. Verify the ECM reference voltage at the sensor connector (usually 5 volts with key on, engine off).

Step 3: Component Replacement and Verification If resistance values are out of specification or the sensor shows physical deterioration, replace the ECT sensor with a genuine Liebherr part. For used machines, always apply dielectric grease to connector terminals before reassembly to prevent future corrosion. Clear the fault code using Liebherr diagnostic software (LiDat) and monitor for code recurrence during a complete heat cycle.

Disclaimer: This guide provides general troubleshooting information. Always consult the official Liebherr service manual for your specific model and consider professional diagnostic assistance for complex electrical issues or if you lack proper diagnostic equipment.