Liebherr Excavator Fault Code E135: Complete Diagnostic Guide

What is Liebherr Fault Code E135?

Liebherr Fault Code E135 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 voltage signals from the coolant temperature sensor that fall outside the manufacturer's specified parameters, typically between 0.5V and 4.5V.

This fault is critical for Liebherr excavators because the ECM relies on accurate coolant temperature data to optimize fuel injection timing, regulate engine protection systems, and control cooling fan operation. On used machines, this code can indicate sensor degradation or wiring issues common in high-hour equipment operating in harsh environments.

Common Symptoms

When Code E135 is active, operators typically experience:

• Check Engine Light or warning lamp illuminated on the instrument cluster
• Engine derate mode engaging, limiting power output to 50-70% to prevent overheating damage
• Cooling fan running continuously at maximum speed regardless of actual engine temperature
• Difficulty starting in cold conditions due to incorrect fuel mapping
• Erratic temperature gauge readings or gauge stuck at minimum/maximum positions

Potential Causes

The most common technical causes for Code E135 on used Liebherr excavators include:

• Coolant temperature sensor failure due to internal resistance drift (common after 5,000+ operating hours)
• Corroded or loose connector pins at the sensor harness connection point near the thermostat housing
• Wiring harness damage from rubbing against engine components, particularly where the harness routes along the cylinder head
• Shorted or open circuit in the sensor signal wire between the sensor and ECM
• ECM internal fault (rare, but possible on machines with 10,000+ hours)
• Low coolant level causing sensor exposure to air instead of coolant

How to Troubleshoot and Fix Code E135

Step 1: Visual Inspection Begin by inspecting the coolant temperature sensor located near the thermostat housing on the engine block. Check for physical damage, coolant leaks, and verify proper coolant level. On used excavators, examine the wiring harness for signs of abrasion, melted insulation, or oil contamination—common at harness support points.

Step 2: Electrical Testing Disconnect the sensor connector and use a digital multimeter to measure sensor resistance. At 68°F (20°C), resistance should read approximately 2,000-3,000 ohms (consult your specific Liebherr service manual for exact values). Test the harness continuity from the sensor connector to the ECM pins, checking for resistance below 5 ohms. Inspect for voltage supply from the ECM—typically 5V reference voltage on the signal wire.

Step 3: Component Replacement and Verification If sensor resistance is out of specification or harness shows open/short conditions, replace the faulty component. For used machines, always apply dielectric grease to connector pins before reassembly to prevent future corrosion. Clear the fault code using Liebherr diagnostic software or a compatible J1939 scan tool, then run the engine through a complete heat cycle to verify repair.

Critical Note for Used Equipment: Before replacing the sensor, inspect connector terminals for "green corrosion" and check harness routing for wear points against engine brackets—these account for 60% of E135 codes on high-hour machines.

---

Disclaimer: This guide provides general troubleshooting information. Always consult the official Liebherr service manual for your specific model and serial number. If unfamiliar with electrical diagnostics, contact a certified Liebherr technician to prevent further damage to electronic components.