What is Liebherr General Fault Code E115?

Fault Code E115 indicates a malfunction in the engine coolant temperature sensor circuit or an implausible coolant temperature reading detected by the Engine Control Module (ECM). This code is triggered when the ECM receives voltage signals outside the expected range from the coolant temperature sensor, or when the sensor readings don't correlate with actual engine operating conditions.

In Liebherr excavators, the coolant temperature sensor plays a critical role in engine management, influencing fuel injection timing, idle speed control, and protective shutdown sequences. When E115 activates, the ECM typically defaults to a pre-programmed substitute value, which can negatively impact fuel efficiency, emissions compliance, and overall engine performance. For used machines, this code often signals sensor degradation or wiring issues common in equipment with significant operating hours.

Common Symptoms

• Warning light illuminated on the instrument cluster, often accompanied by a coolant temperature gauge reading abnormally high or low
• Engine derate mode activated, limiting power output to prevent potential overheating damage
• Hard starting or rough idle, especially during cold starts when the ECM relies heavily on temperature data
• Increased fuel consumption due to the ECM operating with default temperature values instead of actual readings
• Cooling fan running continuously at high speed, regardless of actual engine temperature

Potential Causes

The most common technical causes for E115 on used Liebherr excavators include:

• Coolant temperature sensor failure due to internal element degradation or contamination from coolant additives
• Damaged or corroded wiring harness connections at the sensor plug, particularly where harnesses route near hot exhaust components or moving parts
• Broken or frayed sensor wiring caused by vibration fatigue or rubbing against frame members—common wear points include routing near the engine block mounting brackets
• Corroded or loose ground connections affecting the sensor circuit reference voltage
• ECM internal fault (less common) where the temperature input circuit has failed
• Coolant contamination causing sensor element coating and erratic readings

How to Troubleshoot and Fix Code E115

Step 1: Visual Inspection Begin by locating the coolant temperature sensor, typically installed in the engine block or thermostat housing. Inspect the sensor connector for corrosion, moisture intrusion, or bent pins. On used excavators, pay special attention to the wiring harness routing—check for areas where insulation may have worn through from rubbing against metal surfaces or heat damage from proximity to exhaust manifolds.

Step 2: Electrical Testing Disconnect the sensor and use a digital multimeter to measure resistance across the sensor terminals. Compare readings against Liebherr's specification chart (resistance should decrease as temperature increases—typically 2,000-3,000 ohms at 20°C). Check the harness side for supply voltage (should be approximately 5 volts reference from the ECM) and ensure proper ground continuity with less than 1 ohm resistance to chassis ground.

Step 3: Diagnostic Software Verification Connect Liebherr-specific diagnostic software (such as LiDAT) to monitor live coolant temperature data. Compare the sensor reading with actual engine temperature using an infrared thermometer on the thermostat housing. A variance greater than 10°C indicates sensor failure or ECM calibration issues.

Step 4: Repair or Replace If the sensor tests faulty, replace it with a genuine Liebherr part, applying appropriate thread sealant. For used machines with harness damage, repair affected wiring using heat-shrink solder connections and reroute away from wear points. Clear the fault code and perform a complete warm-up cycle to verify the repair.

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Disclaimer: This guide provides general troubleshooting information. Always consult your Liebherr service manual and consider professional diagnostic assistance for complex electrical issues or if you're unfamiliar with high-voltage systems.