What is XCMG XE750D Fault Code E2571 (SPN4766 FMI16)?

Fault Code E2571 (SPN 4766 FMI 16) indicates a data abnormality or incorrect update rate for the Aftertreatment #1 Diesel Exhaust Fluid Tank Temperature sensor on the XCMG XE750D excavator. This code specifically relates to the Diesel Exhaust Fluid (DEF) system, which is critical for meeting emissions standards on modern Tier 4 Final engines.

SPN 4766 refers to the DEF tank temperature sensor circuit, while FMI 16 indicates that data is valid but updating abnormally—meaning the Engine Control Module (ECM) is receiving signals, but they're either erratic, delayed, or outside expected parameters. For the XE750D's emissions system to function properly, the ECM needs accurate DEF temperature readings to calculate proper injection rates and prevent Selective Catalytic Reduction (SCR) system failures. Ignoring this code can lead to engine derate or shutdown to protect emissions components.

Common Symptoms

• Amber or red warning light illuminated on the instrument cluster, often accompanied by a DEF system fault message
• Engine derate occurring after a predetermined time period, reducing power output by 25-40%
• Poor fuel economy due to improper DEF dosing and incomplete exhaust treatment
• Intermittent fault logging that appears and disappears, especially during temperature fluctuations or machine startup
• DEF quality warning messages appearing even with fresh fluid

Potential Causes

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

• Corroded or damaged wiring harness at the DEF tank temperature sensor connector, particularly where the harness routes near the tank mounting bracket (a known rub point on this model)
• Failed DEF tank temperature sensor due to crystallized DEF contamination or internal sensor element degradation
• Poor electrical ground connection at the DEF system grounding point, often affected by corrosion in high-humidity operating environments
• ECM software version incompatibility or corrupted calibration files after previous repair attempts
• Contaminated or frozen DEF fluid causing erratic temperature readings (common in machines stored improperly or using low-quality DEF)
• Water intrusion into the sensor connector from pressure washing or submersion during operation

How to Troubleshoot and Fix Code E2571

Step 1: Visual Inspection and Connector Check

Begin by locating the DEF tank temperature sensor on the driver's side of the DEF tank. Disconnect the electrical connector and inspect for:

• Corrosion, bent pins, or moisture inside the connector body
• Harness damage along the routing path, especially where it contacts the tank bracket or frame rails
• DEF crystallization around the sensor threads (indicates leakage)

Clean connectors with electrical contact cleaner and apply dielectric grease before reconnecting. On used excavators, this connector often suffers from weather exposure—replacement of the pigtail harness may be necessary if corrosion is severe.

Step 2: Electrical Testing

Using a digital multimeter, perform these checks with the ignition on, engine off:

• Measure supply voltage at the sensor connector: should read approximately 5.0 volts (±0.25V)
• Check sensor resistance: disconnect sensor and measure across terminals—typical range is 1,800-2,500 ohms at 68°F (20°C)
• Test ground circuit continuity from sensor ground pin to battery negative: should read less than 1.0 ohm

If voltage is absent or resistance is out of range, trace the harness back to the ECM checking for breaks or shorts to ground.

Step 3: Sensor Replacement and DEF System Service

If electrical tests pass but the code persists:

• Replace the DEF tank temperature sensor (XCMG part number varies by production date—verify with serial number)
• Drain and inspect DEF fluid quality: contaminated DEF appears cloudy or contains particulates
• Use XCMG diagnostic software or compatible J1939 scan tool to clear codes and monitor live data during a test cycle

For used machines, always check the DEF tank heater operation as well—a failed heater can cause temperature sensor faults during cold starts.

Disclaimer: This guide provides general troubleshooting information. Always consult the XCMG XE750D service manual and consider professional diagnostic assistance for complex electrical issues. Improper repairs to emissions systems may violate environmental regulations.