What is XCMG XE750D Fault Code E1171(1) SPN593 FMI31?

Fault Code E1171(1) SPN593 FMI31 indicates a voltage condition above normal or shorted to high source in the engine's fuel system governor actuator circuit. This code specifically relates to the electronic control module (ECM) detecting an abnormal high voltage signal from the fuel injection control actuator, which regulates fuel delivery and engine speed on the XE750D's diesel power plant.

This fault is critical because the governor actuator directly controls engine performance, fuel efficiency, and power output. When the ECM detects voltage levels exceeding manufacturer specifications (typically above 5V on the reference circuit), it triggers this diagnostic trouble code to prevent potential engine damage or runaway conditions. For the XE750D—a large excavator requiring precise hydraulic control—this malfunction can severely impact operational safety and productivity.

Common Symptoms

• Engine derate mode activated, limiting maximum RPM to 1200-1500 range to protect the engine
• Check engine light or malfunction indicator lamp (MIL) illuminated on the instrument cluster
• Erratic engine speed fluctuations, especially during idle or under load conditions
• Poor throttle response or delayed reaction when operator increases engine speed
• Excessive black smoke from exhaust due to improper fuel metering

Potential Causes

The most common technical failures triggering SPN593 FMI31 on used XE750D excavators include:

• Damaged wiring harness between the ECM and fuel actuator, particularly at routing points near the engine block where vibration causes insulation wear
• Corroded or moisture-infiltrated connectors on the actuator plug (common in machines operating in wet or humid environments)
• Failed fuel governor actuator solenoid with internal short circuit to battery voltage
• ECM internal fault causing incorrect voltage supply to the actuator circuit
• Chafed wires rubbing against frame members or hydraulic lines—a known issue on older XCMG models with 5000+ operating hours

How to Troubleshoot and Fix Code E1171(1) SPN593 FMI31

Step 1: Visual Inspection Begin by thoroughly inspecting the fuel actuator wiring harness from the ECM to the injection pump. On used excavators, focus on areas where the harness passes near moving components or sharp edges. Look for abraded insulation, exposed copper, or evidence of previous repairs. Check all connector pins for corrosion, bent terminals, or moisture intrusion.

Step 2: Electrical Testing Using a digital multimeter (DMM), disconnect the fuel actuator connector and measure resistance between the actuator terminals. Typical resistance should read 3-8 ohms (consult XCMG service manual for exact specifications). Next, check for short to voltage by measuring between each actuator circuit wire and battery positive with ignition on—readings above 0.5V indicate a wiring fault. Test harness continuity from actuator connector back to ECM pins.

Step 3: Component and ECM Verification If wiring tests pass, the actuator solenoid itself may have failed internally. Replace the actuator and clear codes using XCMG diagnostic software or compatible J1939 scan tool. If the fault returns immediately, suspect ECM failure—particularly in machines with extended service life where capacitor degradation causes output driver faults. Before replacing the ECM (an expensive repair on used equipment), verify all ground connections are clean and tight, as poor grounds can mimic voltage faults.

Critical for Used Equipment: Always inspect harness routing after repairs to prevent recurrence. Use protective loom and secure with new tie wraps away from heat and vibration sources.

---

Disclaimer: This guide provides general diagnostic information. Always consult the official XCMG service manual and consider professional assistance for complex electrical diagnostics or ECM programming.