What is XCMG XE750D Fault Code E954(3) SPN1761 FMI1?

Fault Code E954(3) SPN1761 FMI1 indicates a data issue with the Engine Coolant Temperature (ECT) sensor circuit, specifically reporting that the data received is above the normal operating range or experiencing erratic signal behavior. This code is triggered when the Engine Control Module (ECM) detects that coolant temperature sensor readings are implausible or the signal voltage falls outside expected parameters (FMI1 = Data Valid But Above Normal Operating Range).

In the XCMG XE750D excavator, this fault directly impacts the ECM's ability to manage fuel injection timing, engine protection protocols, and hydraulic oil temperature compensation. The coolant temperature sensor provides critical data for preventing overheating and optimizing combustion efficiency, making this code a priority concern for operators of used heavy equipment.

Common Symptoms

• Engine warning light illuminated on the instrument cluster with reduced engine power (derate mode activated)
• Excessive white or black smoke during startup due to improper fuel-air mixture compensation
• Erratic engine idle or difficulty maintaining consistent RPM under load
• Hydraulic system performance degradation as the ECM fails to properly adjust for temperature-related viscosity changes
• Engine protection shutdown occurring prematurely, especially in hot operating conditions

Potential Causes

On used XCMG XE750D excavators, this fault typically stems from:

• Corroded or moisture-damaged connector pins at the coolant temperature sensor (common in machines with 3,000+ operating hours)
• Worn wiring harness near the engine block where vibration causes insulation breakdown and intermittent short circuits
• Failed coolant temperature sensor due to sensor element degradation or contamination from coolant additives
• ECM internal fault or corrupted calibration data (less common but possible in older machines)
• Poor ground connections at the sensor circuit or ECM chassis ground points
• Coolant system issues causing actual overheating that triggers sensor threshold violations

How to Troubleshoot and Fix Code E954(3) SPN1761 FMI1

Step 1: Visual Inspection and Connector Assessment Begin by locating the coolant temperature sensor on the engine block (typically near the thermostat housing). Inspect the sensor connector for corrosion, bent pins, or moisture intrusion. On used excavators, pay special attention to harness chafing points where cables contact the engine block or frame. Clean connectors with electrical contact cleaner and apply dielectric grease.

Step 2: Sensor Circuit Testing Using a digital multimeter, disconnect the sensor and measure resistance across the sensor terminals. At 68°F (20°C), resistance should typically read between 2,000-3,000 ohms (consult XCMG service manual for exact specifications). Check supply voltage at the harness connector with ignition on—it should read approximately 5 volts. Measure ground continuity to ensure less than 1 ohm resistance to chassis ground.

Step 3: Dynamic Testing and Signal Verification Reconnect the sensor and use XCMG diagnostic software or a compatible J1939 scan tool to monitor live coolant temperature data. Compare sensor readings against actual engine temperature using an infrared thermometer. If readings deviate by more than 10°F, replace the sensor. Inspect the wiring harness from sensor to ECM for damage, especially near the engine mounting points where vibration causes wear on used machines.

Step 4: Component Replacement and Verification If testing confirms sensor failure, install an OEM or equivalent quality replacement sensor with proper thread sealant (avoid Teflon tape that can contaminate the coolant). Clear fault codes and perform a cold-to-hot engine cycle to verify proper operation across the full temperature range.

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Disclaimer: This guide provides general troubleshooting information for experienced diesel mechanics. Always consult the official XCMG XE750D service manual and consider professional diagnostic support for complex electrical issues. Improper repairs may cause engine damage or void warranties on used equipment.