What is Liebherr General Fault Code E104?

Liebherr Fault Code E104 indicates a malfunction in the engine coolant temperature sensor circuit or an implausible coolant temperature reading detected by the Electronic Control Module (ECM). This code triggers when the ECM receives voltage signals outside the expected range from the coolant temperature sensor, or when the sensor reading doesn't correlate with actual engine operating conditions.

The coolant temperature sensor is critical for Liebherr excavators because it directly influences fuel injection timing, engine protection protocols, and hydraulic oil temperature management. When E104 appears, the ECM may default to a pre-programmed temperature value, potentially causing suboptimal engine performance and increased wear on components. For used excavators, this code often signals sensor degradation or wiring issues common in machines with higher operating hours.

Common Symptoms

Operators may experience the following when Code E104 is active:

• Engine warning light illuminated on the instrument cluster, sometimes accompanied by a specific coolant temperature warning icon
• Hard starting or extended cranking, especially in cold weather, due to incorrect fuel enrichment
• Engine derate mode activating prematurely, limiting power output and hydraulic performance
• Cooling fan running continuously at high speed, even when engine temperature appears normal
• Black smoke from exhaust during warm-up due to improper fuel-air mixture calculations

Potential Causes

The most common technical reasons for E104 on used Liebherr excavators include:

• Coolant temperature sensor failure due to internal element degradation or contamination from old coolant
• Damaged wiring harness near the sensor connector, particularly at rub points where the harness contacts the engine block or frame
• Corroded or loose electrical connectors at the sensor or ECM, allowing moisture intrusion
• ECM internal fault affecting the sensor input circuit (less common but possible in high-hour machines)
• Coolant system issues causing actual overheating that triggers implausible readings when compared to other sensor data
• Aftermarket sensor installation with incorrect resistance specifications for Liebherr systems

How to Troubleshoot and Fix Code E104

Step 1: Visual Inspection Begin by inspecting the coolant temperature sensor located on the engine block (typically near the thermostat housing). Check the sensor connector for corrosion, bent pins, or moisture. On used excavators, examine the entire wiring harness from sensor to ECM for chafing, particularly where it passes near moving components or sharp edges.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure its resistance at various temperatures. A typical Liebherr coolant sensor reads approximately 2,500-3,000 ohms at 20°C (68°F) and 200-300 ohms at 80°C (176°F). Compare readings to manufacturer specifications. Next, check for supply voltage at the connector (typically 5V reference from ECM) and verify ground continuity.

Step 3: Harness and ECM Verification If the sensor tests correctly, inspect the harness for short circuits or open circuits between the sensor and ECM pins. Use Liebherr diagnostic software (LiDat) to monitor live sensor data and compare with actual coolant temperature using an infrared thermometer. For used machines, pay special attention to connector seal integrity—replace any connectors showing green corrosion.

Step 4: Component Replacement Install a genuine Liebherr coolant temperature sensor if testing reveals sensor failure. After replacement, clear codes using diagnostic software and perform a cold-start test cycle to verify proper operation.

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Disclaimer: This guide provides general troubleshooting information. Always consult Liebherr service documentation and qualified diesel technicians for your specific machine model and serial number before performing repairs.