What is XCMG QSB4.5 CM2150 B108 Fault Code 428?

Fault Code 428 indicates a low voltage condition in the fuel pump solenoid circuit, specifically detecting voltage below the acceptable threshold when the solenoid should be energized. This code is triggered when the Engine Control Module (ECM) on the Cummins QSB4.5 CM2150 engine detects insufficient voltage at the fuel pump solenoid driver circuit, typically below 3 volts when 12+ volts should be present.

This fault is critical for XCMG excavators because the fuel pump solenoid controls fuel delivery pressure and timing. When this circuit malfunctions, the ECM cannot properly regulate fuel flow, directly impacting engine performance, power output, and operational reliability. On used machines, this code often appears due to age-related electrical degradation rather than component failure.

Common Symptoms

• Check Engine Light illuminated on the instrument cluster with possible engine derate mode activated
• Reduced engine power or inability to reach full RPM, especially under load during digging or lifting operations
• Hard starting conditions or extended cranking time, particularly during cold starts
• Rough idle or intermittent stalling when the excavator is at operating temperature
• Fuel delivery inconsistencies causing the machine to surge or hesitate during hydraulic operations

Potential Causes

The most common causes of Code 428 on used XCMG excavators with the CM2150 engine include:

• Corroded or damaged wiring harness connectors at the fuel pump solenoid, particularly where the harness routes near the engine block and experiences heat cycling
• Chafed or broken wires in the solenoid circuit, often found at harness rub points near the fuel pump mounting bracket
• Failed fuel pump solenoid with internal short circuit or high resistance coil winding
• Poor ground connection at the ECM or fuel system ground points due to corrosion buildup
• ECM driver circuit failure, though less common, can occur in high-hour used machines
• Voltage drop in the main power supply caused by failing alternator, weak batteries, or corroded battery terminals

How to Troubleshoot and Fix Code 428

Step 1: Visual Inspection Begin by thoroughly inspecting the fuel pump solenoid harness from the ECM to the solenoid connector. On used excavators, check for wire chafing at known rub points near the fuel pump mounting area and engine vibration zones. Remove the connector at the fuel pump solenoid and inspect for corrosion, bent pins, or moisture intrusion.

Step 2: Electrical Testing Using a digital multimeter, measure the resistance of the fuel pump solenoid coil (typically 2-5 ohms when disconnected). Check for continuity in the wiring from the ECM connector to the solenoid. With the key on and engine off, measure voltage at the solenoid connector during ECM activation—it should read battery voltage (12V+).

Step 3: Ground Circuit Verification Test the ground circuit resistance from the solenoid ground to the battery negative terminal (should be less than 0.5 ohms). Clean all ground connection points at the ECM and engine block, as corrosion is extremely common in used machines operating in dusty or wet conditions.

Step 4: Component Testing and Replacement If wiring and grounds test properly, use Cummins INSITE diagnostic software to perform an actuator test on the fuel pump solenoid. Replace the solenoid if it fails to actuate or shows abnormal current draw. For used excavators with high hours (5,000+), consider replacing the entire solenoid wiring pigtail as preventive maintenance.

Disclaimer: This guide provides general troubleshooting information. Always consult the official XCMG and Cummins service manuals for your specific machine. If you're uncomfortable performing electrical diagnostics, contact a certified Cummins or XCMG service technician to prevent further damage to the fuel system or ECM.