What is XCMG XE750D Fault Code 2612-5 SPN3664 FMI5?

Fault Code 2612-5 (SPN 3664, FMI 5) indicates a current below normal or open circuit condition in the Diesel Exhaust Fluid (DEF) Pump Motor circuit. This fault is triggered when the Engine Control Module (ECM) detects insufficient electrical current flowing to the DEF pump motor, which is responsible for injecting diesel exhaust fluid into the exhaust stream to reduce NOx emissions.

SPN 3664 specifically refers to the DEF pump motor circuit, while FMI 5 designates a current below normal or open circuit failure. In the XCMG XE750D's emissions system, this component is critical for meeting Tier 4 Final emission standards. When this circuit fails, the Selective Catalytic Reduction (SCR) system cannot function properly, potentially triggering engine derate or shutdown to prevent non-compliant operation.

Common Symptoms

When fault code 2612-5 is active on your XE750D, you may experience:

• DEF system warning light illuminated on the instrument cluster with possible amber or red alert
• Engine power derate after a grace period (typically 1-4 hours), reducing machine performance to 50% or lower
• DEF pump fails to operate, with no audible pump priming sound when ignition is turned on
• Exhaust system malfunction warnings displayed on the monitor screen
• Engine may enter limp mode or eventually shut down if the fault persists without correction

Potential Causes

The most common technical reasons for this fault code on used XCMG excavators include:

• Open circuit or broken wiring in the DEF pump motor harness, particularly at flex points near the pump mounting location
• Corroded or loose electrical connectors at the DEF pump motor due to DEF crystallization or moisture intrusion
• Failed DEF pump motor with internal winding damage or seized bearings
• Damaged ECM output driver circuit providing power to the pump motor
• Chafed wiring harness where the DEF system harness routes along the frame or near sharp edges (common wear point on used machines)
• Blown fuse or faulty relay in the DEF pump power supply circuit

How to Troubleshoot and Fix Code 2612-5 SPN3664 FMI5

Step 1: Visual Inspection Begin by thoroughly inspecting the DEF pump wiring harness from the pump to the ECM connector. On used excavators, pay special attention to harness routing near the fuel tank and frame rails where vibration causes wire chafing. Check all connectors for corrosion, bent pins, or DEF crystallization (white crusty deposits). Clean connectors with electrical contact cleaner and ensure tight connections.

Step 2: Electrical Testing Using a digital multimeter, disconnect the DEF pump motor connector and measure resistance across the pump motor terminals. A functional pump typically shows 3-8 ohms resistance. Infinite resistance indicates an open circuit in the motor windings. Next, check for supply voltage at the harness connector with the ignition on—you should see battery voltage (12-14V) when the ECM commands the pump on.

Step 3: Circuit Continuity Check Test continuity between the ECM connector (Pin 47 on most XCMG applications) and the DEF pump connector. Resistance should be less than 1 ohm. Higher resistance or open circuit indicates broken wiring. Check the ground circuit as well, ensuring less than 0.5 ohms to chassis ground.

Step 4: Component Replacement If wiring tests pass but the pump motor shows high resistance or no resistance, replace the DEF pump assembly. For used excavators, always install a new wiring harness connector with the pump to prevent recurring corrosion issues. If all tests indicate proper pump and wiring function, the ECM output driver may be faulty, requiring ECM replacement or repair.

Step 5: Clear Codes and Verify After repairs, use XCMG diagnostic software or a compatible J1939 scan tool to clear fault codes. Perform a DEF pump prime test through the diagnostic software to verify proper operation. Monitor the system for at least one full operating cycle to confirm the repair.

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Disclaimer: This guide provides general troubleshooting information for educational purposes. Always consult the official XCMG service manual for your specific machine serial number and seek assistance from a certified heavy equipment technician for complex electrical diagnostics and repairs. Improper repairs to emission systems may violate environmental regulations.