What is John Deere E240LC Fault Code 000656.06?

Fault Code 000656.06 on the John Deere E240LC indicates a "Swing Motor Temperature Sensor Voltage High" condition. This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) detects an abnormally high voltage signal from the swing motor temperature sensor, typically exceeding 4.5 volts when normal operating range is 0.5-4.5 volts.

This sensor monitors the temperature of the swing motor hydraulic system, which is critical for protecting the excavator's upper structure rotation components from overheating damage. When the ECM receives incorrect temperature data, it cannot properly manage cooling functions or alert operators to genuine overheating conditions, potentially leading to catastrophic swing motor failure or reduced component lifespan on used machines already experiencing wear.

Common Symptoms

• Warning lamp illumination on the instrument cluster with possible audible alarm
• Swing function derate or complete shutdown as a protective measure
• Inaccurate or missing temperature readings on the monitor display
• Intermittent swing operation that may worsen as the machine warms up
• Stored fault code in ECM memory even after symptoms temporarily disappear

Potential Causes

The most common technical causes for this high voltage fault on used E240LC excavators include:

• Open circuit in sensor wiring harness due to wire breakage, particularly at flex points near the swing bearing where repeated rotation causes wear
• Damaged or corroded sensor connector allowing moisture intrusion (common on machines with 3,000+ operating hours)
• Failed swing motor temperature sensor with internal short circuit to supply voltage
• Chafed wiring rubbing against the swing motor housing or hydraulic lines
• ECM internal fault (rare, but possible on high-hour used machines)
• Poor ground connection at the sensor or ECM grounding points

How to Troubleshoot and Fix Code 000656.06

Step 1: Visual Inspection Begin by thoroughly inspecting the swing motor temperature sensor and its wiring harness from the sensor to the ECM. On used excavators, pay special attention to areas where the harness passes through the swing bearing center joint and along the swing motor housing. Look for abraded insulation, pinched wires, corroded connectors, or signs of previous repairs.

Step 2: Sensor and Circuit Testing Disconnect the temperature sensor connector and use a digital multimeter to measure resistance across the sensor terminals. A functioning sensor should show resistance that changes with temperature (typically 2,000-10,000 ohms depending on ambient temperature). An open circuit (infinite resistance) indicates sensor failure. Next, check for supply voltage at the harness connector—you should see approximately 5 volts on the signal wire with ignition on.

Step 3: Wiring Continuity and ECM Check Test continuity from the sensor connector back to the ECM pins using wiring diagrams from John Deere Service Advisor diagnostic software. Check for shorts to 12V supply voltage along the entire harness length. On used machines, remove any protective loom and physically inspect for hidden damage. If wiring and sensor test correctly, suspect ECM malfunction and consider professional ECM testing or replacement.

Critical for Used Equipment: Before ordering new parts, clean all connector pins with electrical contact cleaner and apply dielectric grease to prevent future corrosion. Many high-voltage faults on older excavators resolve with proper connector maintenance.

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Disclaimer: This guide provides general troubleshooting information. Always consult the official John Deere service manual and consider professional diagnostic assistance for complex electrical issues or if you lack proper training and tools.