What is XCMG XE750D Fault Code 15067 SPN678 FMI4?

Fault Code 15067 (SPN 678, FMI 4) indicates a voltage problem below normal range or a short-to-ground condition in the battery voltage circuit of the Engine Control Module (ECM). This code specifically relates to the ECM's monitoring of the main electrical system supply voltage on the XCMG XE750D excavator.

SPN 678 refers to the battery or system voltage sensor circuit, while FMI 4 designates that the voltage has fallen below the acceptable threshold or there's an electrical short to ground. On the XE750D's diesel engine management system, this fault is critical because insufficient battery voltage directly affects the ECM's ability to control fuel injection timing, turbocharger operation, and emission systems. When voltage drops below approximately 9-10 volts during operation, the ECM cannot maintain proper engine performance parameters, potentially causing sudden power loss or complete shutdown.

Common Symptoms

When fault code 15067 is active on your XCMG XE750D, operators typically experience:

• Check Engine Light or malfunction indicator lamp illuminated on the dashboard
• Engine derate mode (reduced power output) or difficulty maintaining RPM under load
• Hard starting conditions, especially after the machine has been sitting overnight
• Intermittent electrical system failures, including flickering displays or instrument cluster resets
• Complete engine shutdown in severe cases, particularly when hydraulic systems are under heavy demand

Potential Causes

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

• Battery degradation – sulfated or weak batteries that cannot maintain adequate voltage under electrical load (extremely common in machines over 5,000 hours)
• Alternator failure or worn voltage regulator unable to maintain 13.8-14.4 volt charging output
• Corroded or loose battery cable connections at terminals, ground points, or ECM power supply connectors
• Damaged wiring harness between alternator and ECM, particularly at flex points near the engine mounting (known wear point on XE750D models)
• Faulty ECM power supply relay or blown fuses in the main power distribution panel
• Parasitic electrical drain from aftermarket accessories or corroded cab wiring (common in older units)

How to Troubleshoot and Fix Code 15067 SPN678 FMI4

Step 1: Verify Battery and Charging System Health

Begin by measuring battery voltage with a digital multimeter. With the engine off, you should read 12.4-12.6 volts across terminals. Start the engine and check voltage at idle – it must rise to 13.8-14.4 volts, indicating proper alternator function. On used excavators, perform a load test; many batteries show acceptable voltage when unloaded but fail under the electrical demands of hydraulic pump operation and ECM power requirements.

Step 2: Inspect All Power Supply Connections

Disconnect battery cables and thoroughly clean all terminals using a wire brush. Check the main ground strap from battery to frame and engine block – corrosion here is a frequent culprit on machines operating in wet or coastal environments. Inspect the positive cable routing from battery through the main fuse panel to the ECM power supply. On the XE750D, pay special attention to the harness connector near the right-side engine mount where cable flex causes internal wire breakage.

Step 3: Test Alternator Output and Voltage Regulation

Using XCMG diagnostic software (or compatible J1939 scan tool), monitor real-time voltage while operating hydraulics. Voltage should not drop below 12.5 volts under maximum electrical load. If voltage fluctuates excessively or drops below threshold, test the alternator output directly at its terminals. Check for worn brushes, failed diodes, or voltage regulator malfunction. Replacement alternators for XE750D models should output minimum 80 amps.

Step 4: Check ECM Power Supply Circuit

Locate the ECM power supply relay in the main electrical panel (consult service manual for exact location). Test relay operation and check for voltage drop across relay contacts. Inspect the ECM connector itself for corrosion, moisture intrusion, or bent pins – particularly critical on used machines where environmental exposure causes connector degradation. Measure voltage directly at the ECM power pins (typically Pin 1 and Pin 2) with engine running; anything below 13 volts indicates circuit resistance issues.

Disclaimer: This guide provides general troubleshooting information for experienced diesel mechanics. Always consult the official XCMG XE750D service manual for model-specific procedures, torque specifications, and safety protocols. If you're purchasing a used excavator displaying this code, have a certified technician perform a comprehensive electrical system evaluation before finalizing the purchase.