XCMG QSX15 Fault Code 110-4: Complete Diagnostic Guide

What is XCMG QSX15 Fault Code 110-4?

Fault Code 110-4 indicates an Engine Coolant Temperature (ECT) Sensor circuit voltage below normal range or shorted to ground. This diagnostic trouble code (DTC) is triggered when the Engine Control Module (ECM) detects abnormally low voltage in the coolant temperature sensor circuit, typically below 0.5 volts.

The ECT sensor is critical for proper engine operation on the QSX15 engine platform. It provides real-time coolant temperature data that the ECM uses to control fuel injection timing, throttle response, and engine protection protocols. When this sensor circuit fails, the ECM enters a default mode that can severely impact machine performance and potentially cause engine damage if ignored.

Common Symptoms

When Code 110-4 is active on your XCMG excavator, you may experience:

• Check Engine Light or Malfunction Indicator Lamp (MIL) illuminated on the instrument cluster
• Engine running in cold start mode continuously, causing rough idle and excessive fuel consumption
• Hard starting or extended cranking times, especially when the engine is warm
• Black smoke from the exhaust due to overfueling from incorrect temperature compensation
• Possible engine derate or power limitation in severe cases to prevent damage

Potential Causes

The most common causes for Code 110-4 on used XCMG excavators include:

• Damaged or corroded wiring harness between the ECT sensor and ECM, particularly at routing points near the engine block where vibration causes harness abrasion
• Failed ECT sensor with internal short circuit to ground (common after 5,000+ operating hours)
• Corroded or loose connector pins at the sensor or ECM connection points due to moisture infiltration
• Shorted sensor ground wire caused by harness rubbing against sharp metal edges or engine components
• ECM internal fault (rare, but possible in high-hour used machines with electrical system history)

How to Troubleshoot and Fix Code 110-4

Step 1: Visual Inspection Begin with a thorough visual examination of the ECT sensor located on the engine coolant outlet housing. Inspect the wiring harness from sensor to ECM for obvious damage, abrasion, or oil contamination. Check connector terminals for corrosion, moisture, or bent pins—common issues in used excavators operating in harsh environments.

Step 2: Electrical Testing Disconnect the ECT sensor connector. Using a digital multimeter (DMM), measure resistance across the sensor terminals. At 68°F (20°C), resistance should read approximately 2,400-2,700 ohms. If readings show 0 ohms (short) or infinite resistance (open), replace the sensor. Check the harness-side connector for voltage: with ignition on and sensor disconnected, you should see approximately 5 volts on the signal wire.

Step 3: Harness Continuity Check For used excavators, perform a continuity test on the sensor harness. Check for shorts to ground by measuring resistance between the signal wire and chassis ground (should be infinite/open circuit). Inspect routing near the turbocharger, exhaust manifold, and frame rails where harness wear is common.

Step 4: Repair and Verification Replace faulty components—prioritize the ECT sensor if testing confirms failure. Repair or replace damaged wiring harness sections using proper gauge wire and heat-shrink connectors. Apply dielectric grease to connector terminals before reassembly. Clear codes using diagnostic software (Cummins INSITE or equivalent) and verify repair with a test run monitoring live coolant temperature data.

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Disclaimer: This guide provides general diagnostic information for Code 110-4. Always consult the XCMG service manual and qualified diesel technicians for machine-specific procedures. Improper diagnosis can lead to engine damage or safety hazards.