What is Liebherr General Fault Code E085?

Liebherr Fault Code E085 indicates a malfunction in the engine coolant temperature sensor circuit or an implausible coolant temperature reading. This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) detects an out-of-range signal, open circuit, short circuit, or irrational temperature value from the coolant temperature sensor (CTS).

This sensor plays a critical role in engine management for Liebherr excavators, as it directly influences fuel injection timing, throttle response, and emission control strategies. When the ECM cannot accurately monitor engine temperature, it may default to a protection mode that limits machine performance to prevent potential engine damage. For used excavators, this code often appears due to sensor degradation, corroded connectors, or wiring harness damage from years of vibration and environmental exposure.

Common Symptoms

When Code E085 is active, operators typically experience:

• Check engine light or malfunction indicator lamp illuminated on the dashboard
• Engine derate or limited power output as the ECM enters failsafe mode
• Hard starting or rough idle, especially when the engine is cold
• Poor fuel economy and black smoke from the exhaust due to improper fuel mixture
• Erratic temperature gauge readings or temperature gauge stuck at minimum/maximum values

Potential Causes

The most common technical causes for E085 in Liebherr excavators include:

• Faulty coolant temperature sensor due to internal element failure or contamination
• Damaged wiring harness at known rub points near the engine block or along the frame rail
• Corroded or loose electrical connectors at the sensor or ECM, especially in machines with high operating hours
• Short circuit to ground or power in the sensor signal wire
• ECM internal fault (rare, but possible in older machines)
• Coolant contamination affecting sensor accuracy or low coolant level exposing the sensor

How to Troubleshoot and Fix Code E085

Step 1: Visual Inspection Begin by inspecting the coolant temperature sensor location on the engine block. Check for physical damage, coolant leaks, or corrosion on the connector terminals. On used excavators, pay special attention to wiring harness condition where it routes near hot engine components or sharp edges.

Step 2: Electrical Testing Disconnect the sensor and measure its resistance using a digital multimeter. Compare readings against Liebherr specifications (typically 2,000-3,000 ohms at 20°C). Test the wiring harness for continuity between the sensor connector and ECM pins, and check for shorts to ground using the ohmmeter function.

Step 3: Signal Verification With the sensor connected, use Liebherr diagnostic software (LiDat or compatible scan tool) to monitor live coolant temperature data. Compare the sensor reading to actual engine temperature using an infrared thermometer. A variance greater than 10°C indicates sensor failure.

Step 4: Repair and Verification Replace the faulty coolant temperature sensor with a genuine Liebherr part, ensuring proper torque specifications. If wiring damage is found, repair using heat-shrink solder connections and protect with split loom. Clear the fault code, run the engine through a complete warm-up cycle, and verify the code does not return.

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Disclaimer: This guide provides general troubleshooting information. Always consult the official Liebherr service manual for your specific model and consider engaging a certified Liebherr technician for complex diagnostics or repairs on used machinery.