What is XCMG XE750D Fault Code 3118-5 SPN4374 FMI5?

Fault Code 3118-5 (SPN 4374, FMI 5) indicates an open circuit or abnormally high electrical resistance in the Diesel Particulate Filter (DPF) Outlet Temperature Sensor circuit. This code is triggered when the Engine Control Module (ECM) detects that the sensor responsible for monitoring exhaust temperature downstream of the DPF is not providing a valid signal due to circuit interruption or excessive resistance.

This sensor is critical for the XE750D's emissions system because it monitors regeneration effectiveness and prevents overheating. On this Cummins-powered excavator, accurate DPF outlet temperature readings ensure proper regeneration cycles and protect the aftertreatment system from thermal damage. When this circuit fails, the ECM cannot verify DPF function, potentially triggering derate modes that limit machine performance to protect the engine.

Common Symptoms

• Amber or red exhaust system warning lamp illuminated on the instrument cluster
• Engine power derate (reduced horsepower output, typically 25-40% reduction)
• Regeneration inhibit condition – machine may not complete automatic DPF regeneration cycles
• Persistent audible alarm when engine attempts regeneration without valid temperature feedback
• Increased fuel consumption as the ECM enters failsafe mode with conservative fuel mapping

Potential Causes

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

• Corroded or damaged sensor connector at the DPF outlet temperature probe (exhaust heat and moisture exposure accelerate corrosion)
• Broken or chafed wiring harness between the sensor and ECM, particularly where the harness routes near the turbocharger or exhaust components
• Failed temperature sensor element due to thermal cycling fatigue (common after 4,000-6,000 operating hours)
• ECM connector pin corrosion at terminal locations corresponding to SPN 4374
• Aftermarket harness repairs using incorrect wire gauge or inadequate heat shielding

How to Troubleshoot and Fix Code 3118-5 SPN4374 FMI5

Step 1: Visual Inspection Locate the DPF outlet temperature sensor on the exhaust pipe immediately after the DPF canister. Inspect the sensor connector for corrosion, bent pins, or moisture intrusion. Check the wiring harness for abrasion points where it contacts frame members or exhaust components – this is especially critical on used machines with 3,000+ hours.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure resistance across the sensor terminals. A functional sensor should read approximately 1,500-2,500 ohms at room temperature (refer to XCMG service manual for exact specifications). If reading shows infinite resistance (open circuit) or erratic values, replace the sensor.

Step 3: Circuit Continuity Check With the sensor disconnected, measure continuity and resistance from the harness connector back to the ECM pins. Resistance should be less than 5 ohms. Check for shorts to ground. On used excavators, carefully inspect harness routing – previous repairs may have eliminated protective conduit or heat shielding.

Step 4: Connector Service Clean all connector terminals with electrical contact cleaner and apply dielectric grease to prevent future corrosion. Replace any connectors showing heat damage or melted housings.

Step 5: Clear Code and Verify After repairs, use XCMG diagnostic software or a compatible J1939 scan tool to clear the fault code. Operate the machine through a complete work cycle and monitor for code recurrence.

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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.