What is XCMG XE750D Fault Code 3100-2 SPN3516 FMI2?

Fault Code 3100-2 (SPN 3516, FMI 2) indicates a data error or erratic signal from the Actuator #4 (Engine Fuel Valve) circuit in the XCMG XE750D excavator's Engine Control Module (ECM). This code specifically relates to the fuel metering actuator that controls fuel delivery to the diesel engine's high-pressure fuel injection system.

SPN 3516 refers to the Actuator #4 position sensor or control circuit, while FMI 2 indicates "data erratic, intermittent, or incorrect." This fault directly impacts the ECM's ability to precisely regulate fuel injection timing and volume, which is critical for maintaining proper engine performance, emissions compliance, and fuel efficiency on this 75-ton class excavator. When active, the system may enter a derated power mode to prevent engine damage.

Common Symptoms

• Engine derate warning light illuminated on the dashboard with noticeable power loss during digging or swing operations
• Rough idling or inconsistent engine RPM fluctuations, especially under load
• Black smoke from exhaust due to improper fuel metering and incomplete combustion
• Intermittent engine hesitation or delayed throttle response when operating hydraulic functions
• Check engine light (MIL) remains active even after machine restart

Potential Causes

The most common technical causes for this fault code on used XCMG XE750D excavators include:

• Corroded or loose electrical connectors at the fuel actuator harness (common wear point near engine block vibration zones)
• Damaged wiring harness with chafed insulation due to contact with engine components or frame rails
• Failed fuel metering actuator solenoid caused by internal coil degradation or contaminated diesel fuel
• Faulty ECM calibration data or corrupted software requiring reflashing
• Low voltage supply to the actuator circuit from battery or alternator issues (check for voltage drops below 22V on 24V systems)
• Contaminated fuel system causing mechanical binding of the actuator valve mechanism

How to Troubleshoot and Fix Code 3100-2 SPN3516 FMI2

Step 1: Visual Inspection of Wiring and Connectors Begin by inspecting the fuel actuator wiring harness running from the ECM to the fuel injection pump. On used excavators, check for rubbing points where the harness contacts the engine block or hydraulic lines. Look for green corrosion on connector pins at the actuator—a common issue in machines operating in humid environments. Clean connectors with electrical contact cleaner and apply dielectric grease.

Step 2: Electrical Testing with Multimeter Disconnect the actuator connector and perform a resistance check across the actuator solenoid terminals. Typical readings should be 2-6 ohms (consult XCMG service manual for exact specs). Next, check for voltage supply at the harness connector with ignition on—should read approximately 24V DC. Test for continuity between ECM connector pins and actuator harness to identify any open circuits.

Step 3: Signal Testing with Diagnostic Software Connect XCMG diagnostic software (or compatible J1939 diagnostic tool) to monitor real-time actuator position data. Command the actuator through its full range while monitoring actual vs. commanded position. Erratic readings exceeding ±5% deviation indicate actuator failure. Check for intermittent signal dropouts by wiggling harness connections during testing.

Step 4: Component Replacement or Calibration If electrical tests pass but the code persists, replace the fuel metering actuator assembly. For used machines, always inspect the fuel filter condition and drain water separators before installing new parts—contaminated fuel accelerates actuator wear. After replacement, perform ECM fuel system calibration using manufacturer software and clear all fault codes.

Disclaimer: This guide provides general troubleshooting information. Always consult the official XCMG service manual and consider professional diagnosis for complex fuel system repairs. Improper fuel system work may cause engine damage or safety hazards.