What is XCMG XE6D125-6D140-6D170 CM2350 Fault Code 155?

Fault Code 155 indicates an Injector Cylinder 6 - Mechanical System Not Responding Properly or Out of Adjustment. This code is triggered when the Engine Control Module (ECM) detects that the fuel injector for cylinder 6 is not operating within the expected mechanical parameters during fuel delivery cycles.

In the Cummins CM2350 engine platform used in XCMG excavators, this fault specifically relates to the electronic unit injector (EUI) system's inability to maintain proper fuel metering or timing on cylinder 6. The ECM monitors injector performance through actuator response data and fuel pressure feedback. When the injector's mechanical response deviates from commanded values—often due to internal wear, sticking components, or calibration drift—Code 155 is logged. This is critical because improper fuel delivery causes power loss, increased emissions, and potential damage to the piston and cylinder head on cylinder 6.

Common Symptoms

• Engine misfiring or rough idle, particularly noticeable under load during digging or lifting operations
• Black or white smoke from the exhaust, indicating incomplete combustion in cylinder 6
• Power derate mode activated, limiting machine performance to prevent further engine damage
• Check Engine Light (CEL) illuminated on the instrument cluster with stored diagnostic trouble codes
• Increased fuel consumption and reduced hydraulic system responsiveness due to inconsistent engine output

Potential Causes

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

• Worn or sticking injector plunger inside the cylinder 6 fuel injector, common in machines with 5,000+ operating hours
• Contaminated fuel causing varnish buildup or debris lodged in the injector nozzle orifice
• Faulty injector solenoid or damaged wiring harness to cylinder 6 injector—check for harness abrasion near the engine block mounting points
• Low fuel pressure from a failing fuel transfer pump or restricted fuel filters
• ECM calibration issues or corrupted injector trim codes following previous repairs or ECM replacement
• Mechanical timing problems with the injector camshaft or rocker arm assembly specific to cylinder 6

How to Troubleshoot and Fix Code 155

Step 1: Verify Fault Code and Perform Visual Inspection Connect Cummins INSITE diagnostic software or compatible scan tool to retrieve active and inactive codes. Perform a thorough visual inspection of the injector wiring harness for cylinder 6, checking for chafing, corrosion on connectors, or oil contamination at the injector solenoid connector. On used excavators, harness wear near heat shields is extremely common.

Step 2: Test Injector Electrical Circuit With the engine off and injector connector disconnected, use a digital multimeter to measure solenoid resistance (typically 0.3-2.0 ohms depending on injector type). Check for supply voltage (battery voltage when cranking) and proper ground continuity at the ECM connector. Inspect the ECM injector driver circuit for shorts or opens.

Step 3: Perform Injector Cut-Out Test Using INSITE software, perform a cylinder cut-out test to isolate cylinder 6. If engine performance doesn't change when cylinder 6 is disabled, the injector is likely mechanically failed. Check fuel pressure at the injector inlet (should be 50-70 PSI during cranking).

Step 4: Remove and Inspect Injector Remove the cylinder 6 injector following manufacturer torque specifications. Inspect for carbon buildup, damaged O-rings, or scoring on the injector body. On used machines, replace all seals and copper washers regardless of appearance. Send injector for professional flow bench testing or replace with a remanufactured unit with updated injector calibration codes.

Step 5: Clear Codes and Verify Repair After repair, program new injector trim codes into the ECM using INSITE. Clear all fault codes, perform a regeneration cycle if equipped with DPF, and test under load.

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Disclaimer: This guide provides general diagnostic information. Always consult the official XCMG service manual and Cummins troubleshooting procedures. For used excavators with complex electrical or fuel system issues, professional diagnosis by a certified Cummins technician is recommended.