XCMG (B5.9, C8.3 Engine) Fault Code 155: Expert Diagnostic Guide

What is XCMG Fault Code 155?

Fault Code 155 indicates an Injector Cylinder #5 Circuit Malfunction, signaling that the Engine Control Module (ECM) has detected an abnormal electrical condition in the fuel injector circuit for cylinder number five. This code is specific to XCMG excavators equipped with Cummins B5.9 or C8.3 diesel engines, where precise fuel delivery is critical for maintaining power output and emissions compliance.

This fault directly impacts the engine's ability to properly meter fuel to the fifth cylinder, causing combustion imbalance and reduced efficiency. In used excavators, this code often results from degraded wiring harnesses or injector solenoid failures—common issues in machines with extended operating hours in harsh construction environments.

Common Symptoms

When Code 155 is active, operators typically experience:

• Rough idling or noticeable engine vibration, particularly at lower RPMs
• Reduced engine power (derate mode) with loss of hydraulic performance during heavy digging operations
• Black or white exhaust smoke indicating incomplete combustion in cylinder #5
• Check Engine Light (CEL) illuminated on the instrument cluster
• Increased fuel consumption with uneven engine running characteristics

Potential Causes

The most common technical causes for Code 155 in used XCMG excavators include:

• Faulty fuel injector solenoid on cylinder #5 (internal coil failure or mechanical sticking)
• Damaged injector wiring harness, especially at known rub points near the valve cover or engine block
• Corroded or loose electrical connectors at the injector or ECM connection points
• ECM internal driver circuit failure (less common but possible in high-hour machines)
• Poor ground connections due to corrosion or loose mounting bolts
• Injector mechanical failure causing electrical feedback to the ECM

How to Troubleshoot and Fix Code 155

Step 1: Visual Inspection Begin by thoroughly inspecting the injector wiring harness for cylinder #5. Look for abrasion marks, melted insulation, or damage where the harness contacts the engine block or valve cover. Check all electrical connectors for corrosion, bent pins, or moisture intrusion—critical on used machines with compromised seals.

Step 2: Electrical Testing Using a digital multimeter, measure the resistance of the #5 injector solenoid (typically 0.3-2.0 ohms for Cummins injectors; consult service manual for exact specs). Disconnect the injector connector and check for continuity to ground—there should be none. Test the supply voltage from the ECM during cranking (should read battery voltage when activated).

Step 3: Injector Swap Test Swap the #5 injector with an adjacent cylinder (such as #3 or #6). Clear codes and operate the machine. If Code 155 moves to the new cylinder location, the injector itself is faulty. If the code remains at cylinder #5, suspect wiring or ECM issues.

Step 4: Harness and Connector Repair For used excavators, repair or replace damaged sections of the injector harness. Use dielectric grease on all connectors and ensure proper routing away from heat sources and moving components. Verify all ground connections are clean and tight.

Step 5: Component Replacement Replace the faulty injector or repair the harness as identified. After repairs, use Cummins INSITE or compatible diagnostic software to clear codes and perform an injector cutout test to verify proper operation of all cylinders.

---

Disclaimer: This guide provides general troubleshooting information. Always consult the manufacturer's service manual and consider professional diagnostic assistance for complex electrical issues. Improper repairs can cause engine damage or safety hazards.