What is Liebherr General Fault Code E079?

Liebherr Fault Code E079 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 voltage signals outside the normal operating range from the coolant temperature sensor or identifies a temperature reading that doesn't correlate with other engine parameters.

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 this sensor circuit fails, the ECM cannot accurately monitor engine thermal conditions, potentially leading to overheating, reduced performance, or unnecessary engine derating to prevent damage.

Common Symptoms

When Code E079 is active, operators typically experience:

• Warning light illumination on the instrument cluster, often accompanied by a coolant temperature alert symbol
• Engine derate or power reduction as the ECM enters a fail-safe mode to protect the engine from potential thermal damage
• Erratic temperature gauge readings that fluctuate abnormally or remain fixed at minimum/maximum positions
• Difficulty starting in cold conditions, as the ECM cannot properly adjust fuel delivery without accurate temperature data
• Increased fuel consumption due to improper fuel mapping when the ECM uses default temperature values

Potential Causes

The most common technical causes for E079 on used Liebherr excavators include:

• Worn or corroded sensor connector pins at the coolant temperature sensor, particularly common in machines with 5,000+ operating hours
• Damaged wiring harness near the engine block where vibration and heat cycles cause insulation breakdown and wire chafing
• Failed coolant temperature sensor due to internal element degradation or contamination from coolant additives
• Low coolant levels causing air pockets around the sensor, resulting in inaccurate readings
• ECM internal fault or corrupted calibration data (less common but possible in older machines)
• Corroded ground connections affecting the sensor's reference voltage circuit

How to Troubleshoot and Fix Code E079

Step 1: Visual Inspection Begin by inspecting the coolant temperature sensor and its wiring harness for obvious damage. On used excavators, check connector terminals for corrosion, bent pins, or moisture intrusion. Examine the harness routing near the engine block where heat and vibration commonly cause insulation wear.

Step 2: Verify Coolant Level and Condition Ensure the cooling system is properly filled and the sensor is fully submerged in coolant. Low coolant levels can cause intermittent E079 codes. Check for air pockets by bleeding the system according to Liebherr specifications.

Step 3: Electrical Testing Using a digital multimeter, disconnect the sensor and measure its resistance at various temperatures. A typical coolant temperature sensor shows approximately 2,500-3,000 ohms at 20°C (68°F) and 200-300 ohms at 80°C (176°F). Compare readings against Liebherr's specifications in the service manual.

Step 4: Circuit Voltage Check With the sensor disconnected and ignition on, measure supply voltage at the sensor connector. You should see approximately 5 volts from the ECM. If voltage is absent or incorrect, trace the harness for breaks or shorts to ground.

Step 5: Component Replacement If sensor resistance values are out of specification or the sensor shows physical damage, replace it with a genuine Liebherr part. For used machines, always replace the connector pigtail simultaneously, as corrosion often compromises connection integrity even after sensor replacement.

Step 6: Clear Code and Monitor After repairs, use Liebherr diagnostic software (LiDat) or compatible scan tool to clear the fault code. Run the machine through a complete thermal cycle and monitor for code recurrence.

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Disclaimer: This guide provides general troubleshooting information for Liebherr excavators. Always consult the manufacturer's service manual for your specific model and serial number. Complex electrical diagnostics should be performed by qualified technicians with proper training and equipment. Improper repairs may result in further damage or safety hazards.