What is Liebherr General Fault Code E105?

Fault Code E105 on Liebherr excavators indicates a malfunction in the engine coolant temperature sensor circuit or an out-of-range coolant temperature reading. This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) detects either an implausible voltage signal from the coolant temperature sensor (CTS) or readings that fall outside the predetermined operational parameters.

The coolant temperature sensor plays a critical role in Liebherr's engine management system by providing real-time data that influences fuel injection timing, idle speed control, and engine warm-up protocols. When E105 activates, the ECM typically defaults to a pre-programmed "limp mode" value, which can significantly impact machine performance, fuel efficiency, and component longevity. For used excavators, this code often surfaces due to sensor degradation, wiring harness damage from engine vibration, or corrosion at connection points—issues that become increasingly common as machines accumulate operating hours.

Common Symptoms

When fault code E105 is active, operators typically experience:

• Check Engine Light or malfunction indicator lamp illuminated on the instrument panel
• Hard starting or extended cranking time, especially during cold starts
• Rough idling or erratic engine RPM fluctuations when the machine is warming up
• Reduced engine power or activation of derate mode to prevent potential overheating damage
• Inaccurate temperature gauge readings showing unusually high or low coolant temperatures

Potential Causes

The most common technical reasons for E105 in used Liebherr excavators include:

• Faulty coolant temperature sensor with internal resistance drift due to thermal cycling and age
• Damaged or corroded wiring harness connections at the sensor connector, particularly where harnesses contact the engine block
• Chafed or pinched sensor wires along routing paths near the thermostat housing—a known wear point on older machines
• Contaminated coolant causing sensor element fouling or deposits on the sensor tip
• ECM internal circuit failure (rare, but possible in high-hour machines)
• Intermittent open or short circuits in the sensor ground path

How to Troubleshoot and Fix Code E105

Step 1: Visual Inspection Begin by locating the coolant temperature sensor (typically threaded into the thermostat housing or cylinder head). Inspect the sensor connector for corrosion, bent pins, or moisture intrusion. Check the wiring harness for obvious damage, abrasion points where it contacts metal surfaces, or heat damage near exhaust components. For used excavators, pay special attention to harness friction points and zip-tie mounting locations that may have loosened over time.

Step 2: Electrical Testing Disconnect the sensor connector and use a digital multimeter to measure sensor resistance. At 68°F (20°C), resistance should typically read between 2,000-3,000 ohms (consult your specific Liebherr service manual for exact specifications). Test the harness voltage supply from the ECM with the key on, engine off—you should see approximately 5 volts reference voltage. Check continuity between the sensor ground pin and chassis ground.

Step 3: Advanced Diagnostics Connect Liebherr's proprietary diagnostic software (LiDat or compatible scan tool) to monitor live coolant temperature data. Compare the sensor reading against actual coolant temperature using an infrared thermometer. A variance greater than 10°F indicates sensor failure. If sensor and harness test properly, perform a wiggle test while monitoring live data to identify intermittent connections.

Step 4: Repair and Verification Replace the coolant temperature sensor if resistance values are out of specification or if physical damage is evident. Repair or replace damaged harness sections, ensuring proper routing away from heat sources and moving components. Apply dielectric grease to connector pins to prevent future corrosion. Clear the fault code using diagnostic software and perform a complete warm-up cycle to verify the repair.

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Disclaimer: This guide provides general troubleshooting information for Liebherr fault code E105. Always consult the specific service manual for your machine model and serial number. If you're unfamiliar with electrical diagnostics or lack proper tools, consult a certified Liebherr technician to prevent misdiagnosis or additional damage to your used excavator.