What is XCMG XE750D Fault Code 110-3 SPN110 FMI3?

Fault Code 110-3 (SPN110 FMI3) indicates a voltage above normal or shorted high condition in the Engine Coolant Temperature (ECT) sensor circuit. This code is part of the J1939 diagnostic protocol used in modern diesel engines, where SPN110 specifically identifies the coolant temperature parameter, and FMI3 signals that the Engine Control Module (ECM) is receiving abnormally high voltage from the sensor circuit.

This fault is critical for the XCMG XE750D because the ECM relies on accurate coolant temperature data to manage engine timing, fuel injection, and protective shutdown systems. When this sensor circuit malfunctions, the engine may enter derate mode or fail to start, directly impacting productivity on the jobsite.

Common Symptoms

• Check Engine Light or engine warning indicator illuminated on the instrument cluster
• Engine enters power derate mode, limiting maximum RPM and hydraulic performance
• Hard starting or rough idle, especially during cold starts
• ECM defaults to substitute values, causing poor fuel economy and excessive black smoke
• In severe cases, the engine may trigger emergency shutdown protocols to prevent overheating damage

Potential Causes

The most common technical causes for Code 110-3 on used XCMG excavators include:

• Shorted ECT sensor wiring harness, particularly where cables route near sharp edges or hot exhaust components (common wear point behind the cylinder head)
• Failed Engine Coolant Temperature sensor with internal short circuit
• Corroded or moisture-damaged connectors at the sensor plug (frequently seen in machines operating in wet or coastal environments)
• Damaged ECM pins or internal ECM fault (less common, but possible in high-hour used machines)
• Aftermarket or incorrect replacement sensor with wrong resistance specifications

How to Troubleshoot and Fix Code 110-3 SPN110 FMI3

Step 1: Visual Inspection
Inspect the ECT sensor and its wiring harness for obvious damage, melted insulation, or coolant contamination. On used excavators, check for harness abrasion where cables contact frame components or engine mounts.

Step 2: Test the Sensor
Disconnect the ECT sensor connector and measure resistance across the sensor terminals using a digital multimeter. At room temperature (68°F/20°C), resistance should typically read 2,000-3,000 ohms (consult XCMG service manual for exact specs). If resistance is near zero ohms, the sensor is shorted internally.

Step 3: Check Circuit Voltage
With the sensor disconnected and ignition on, measure voltage at the harness connector. You should see approximately 5 volts reference voltage from the ECM. If voltage reads battery voltage (12-24V), there's a short to power in the harness.

Step 4: Inspect Connectors and Harness
Examine all connectors for corrosion, bent pins, or moisture intrusion. On used machines, apply dielectric grease after cleaning. Trace the harness for rub-through points, especially near the engine block and valve cover.

Step 5: Replace Faulty Components
Install a genuine XCMG ECT sensor if testing confirms failure. If harness damage is found, repair with high-temperature automotive wire and heat-shrink tubing, or replace the entire harness section.

Disclaimer: This guide provides general diagnostic procedures. Always consult the official XCMG service manual and consider professional evaluation by a certified technician, especially for complex electrical diagnostics or ECM replacement decisions.