XCMG QSX15 Fault Code 153: Complete Diagnostic & Repair Guide

---

What is XCMG QSX15 Fault Code 153?

XCMG QSX15 Fault Code 153 indicates a fault in the Engine Coolant Temperature (ECT) Sensor Circuit — specifically, the signal voltage has fallen below the acceptable lower threshold, triggering an out-of-range low condition.

This code is generated by the ECM (Engine Control Module) when the voltage signal from the coolant temperature sensor drops below approximately 0.2V DC, suggesting an open circuit, a failed sensor, or a wiring fault. On the Cummins QSX15 engine platform used in XCMG heavy excavators, accurate coolant temperature data is critical for managing fuel injection timing, cooling fan engagement, and engine protection strategies. An unresolved Code 153 can lead to improper engine temperature management, risking overheating or unnecessary derating.

---

Common Symptoms

When Fault Code 153 is active on the XCMG QSX15, operators typically report:

• Amber or red warning light illuminated on the instrument cluster
• Engine derate mode engaged, limiting RPM and hydraulic output
• Coolant temperature gauge reading abnormally low or stuck at zero even after warm-up
• Cooling fan running continuously at full speed regardless of actual temperature
• Intermittent fault logging with no clear pattern, especially in cold or wet operating conditions

---

Potential Causes

The following are the most common technical causes for this fault code, particularly on used or high-hour XCMG QSX15 machines:

• Failed ECT sensor — internal resistance has drifted out of specification
• Open circuit in the sensor signal wire — common at harness flex points near the engine block
• Corroded or backed-out connector pins at the sensor plug or ECM harness connector
• Chafed or damaged wiring harness where it routes near exhaust components or frame edges
• Previous repair work that left splice joints unprotected, leading to moisture intrusion

---

How to Troubleshoot and Fix Code 153

Step 1 — Perform a Visual Harness Inspection Before touching any components, inspect the wiring harness running from the ECT sensor to the ECM. On used excavators, look specifically for harness friction wear, heat damage near the exhaust manifold, and corroded connector bodies. Clean all connector pins with electrical contact cleaner and check for bent or backed-out terminals.

Step 2 — Test the ECT Sensor Resistance Disconnect the sensor connector and use a digital multimeter to measure sensor resistance across the two signal terminals. At ambient temperature (~25°C), a healthy QSX15 ECT sensor should read approximately 2,000–3,000 ohms. A reading of infinite resistance (OL) confirms an open/failed sensor requiring replacement.

Step 3 — Check Circuit Continuity and Voltage Supply With the key in the ON position (engine off), use a multimeter to verify 5V reference voltage at the sensor connector from the ECM side. Then check circuit continuity between the sensor harness connector and the ECM pin. Any break confirms a wiring fault rather than a sensor fault.

Step 4 — Clear Codes and Verify with Diagnostic Software After repairs, use Cummins INSITE or compatible OEM diagnostic software to clear the fault code and monitor live ECT sensor data during engine warm-up. Confirm the reading climbs steadily from ambient to normal operating temperature (~85–95°C).

---

Disclaimer: This guide is intended for qualified heavy equipment mechanics and experienced operators. Always follow XCMG and Cummins OEM service documentation for your specific machine configuration. If you are unsure about any diagnostic step, consult a certified diesel technician or authorized XCMG service center before performing repairs.