What is XCMG XE750D Fault Code 110-4 (SPN110 FMI4)?

Fault Code 110-4 (SPN 110 FMI 4) indicates that the Engine Coolant Temperature (ECT) sensor circuit is experiencing a voltage signal below the normal operating range on your XCMG XE750D excavator. This diagnostic trouble code (DTC) is triggered when the Engine Control Module (ECM) detects an abnormally low voltage reading from the coolant temperature sensor circuit, typically below 0.5 volts.

SPN 110 specifically references the engine coolant temperature parameter, while FMI 4 designates a "voltage below normal or shorted to ground" condition. This code is critical because the ECM relies on accurate coolant temperature data to control fuel injection timing, engine warm-up cycles, and fan engagement. On the XE750D's diesel engine, incorrect temperature readings can lead to poor fuel economy, excessive emissions, and potential engine damage from improper combustion timing.

Common Symptoms

When fault code 110-4 is active on your XCMG XE750D, operators typically experience:

• Check Engine Light (CEL) or malfunction indicator lamp illuminated on the instrument cluster
• Engine running rich with black smoke from the exhaust due to ECM defaulting to cold-start fuel maps
• Cooling fan running continuously at high speed, even when engine is cold
• Difficult cold starts or extended cranking time in normal temperatures
• Power derate mode engaged in some cases, limiting hydraulic performance and travel speed

Potential Causes

The most common technical reasons for code 110-4 on used XCMG excavators include:

• Damaged or corroded ECT sensor connector – particularly common on machines operating in wet or corrosive environments
• Shorted sensor wiring harness – wires rubbing against engine block or frame rails near the thermostat housing
• Failed coolant temperature sensor – internal short circuit causing constant low voltage signal
• Damaged ECM wiring or corrosion at the ECM connector pins (typically pins related to sensor ground circuits)
• Poor ground connection at engine block ground strap or sensor mounting point
• Coolant contamination causing sensor element degradation in older machines

How to Troubleshoot and Fix Code 110-4

Step 1: Visual Inspection Begin by locating the ECT sensor, typically mounted near the thermostat housing on the engine block. Inspect the sensor connector for corrosion, bent pins, moisture intrusion, or physical damage. On used excavators, check for harness chafing where wiring routes near moving components or sharp edges. Clean all connector contacts with electrical contact cleaner and dielectric grease.

Step 2: Electrical Testing Disconnect the ECT sensor connector. Using a digital multimeter (DMM), measure resistance across the sensor terminals. A functional sensor should read approximately 2,000-3,000 ohms at 68°F (20°C). Next, check for continuity to ground on the signal wire with the sensor disconnected—any continuity indicates a short circuit in the harness. Measure supply voltage at the ECM connector (typically 5 volts reference) to ensure the ECM is providing proper power.

Step 3: Component Replacement and Verification If testing confirms a faulty sensor, replace the ECT sensor using OEM or high-quality aftermarket parts rated for diesel applications. Torque to manufacturer specifications (typically 8-12 ft-lbs) and apply thread sealant to prevent coolant leaks. If wiring is damaged, repair using weatherproof butt connectors and heat shrink tubing, ensuring proper routing away from heat sources. Clear fault codes using XCMG diagnostic software or compatible scan tool, then monitor for code recurrence during a full heat cycle.

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Disclaimer: This guide provides general diagnostic information for educational purposes. Always consult the XCMG XE750D service manual and consider professional diagnostics for complex electrical issues, especially on used machinery with unknown maintenance history.