What is XCMG XE750D Fault Code 45662 SPN651 FMI5?

Fault Code 45662 (SPN651 FMI5) indicates a current below normal or open circuit condition in the J1939 Data Link, specifically affecting the engine's CAN communication system. This code is triggered when the Electronic Control Module (ECM) detects insufficient electrical current flowing through the Controller Area Network (CAN) bus circuit, which is the critical digital backbone allowing the engine controller to communicate with other machine systems.

For the XCMG XE750D excavator, this fault directly impacts the J1939 network that connects the engine ECM to the machine's display, hydraulic controllers, and diagnostic ports. When this communication pathway fails, the engine management system cannot properly share sensor data, receive commands, or report operational parameters. This is particularly critical on this model because the integrated hydraulic-engine control strategy relies on seamless CAN bus communication to optimize fuel efficiency and power delivery during heavy digging operations.

Common Symptoms

• Warning lights on the instrument cluster, specifically the amber "Check Engine" or "Diagnostic" lamp illuminating continuously
• Loss of engine data on the operator display—RPM, coolant temperature, or fuel rate may show dashes or freeze at last known values
• Intermittent engine derating where power output suddenly reduces to 75% or enters limp-home mode without clear pattern
• Failure of electronic diagnostics to connect via service ports, making code reading difficult or impossible
• Erratic gauge behavior with needles jumping or digital readouts flickering during machine operation

Potential Causes

Wiring harness damage is the primary culprit in used XE750D machines, particularly where the main engine harness runs along the right side frame rail near the hydraulic tank—this known rub point causes insulation wear and exposes the CAN wires (typically twisted orange/green pair) to grounding against the chassis.

Corroded connector terminals at the ECM bulkhead connector (C1) or the diagnostic port connection, especially on machines operated in coastal or high-humidity environments where salt and moisture penetrate the Deutsch-style connectors.

Failed termination resistors within the CAN network—the J1939 bus requires 120-ohm resistors at each network end, and these can fail in older machines, causing signal reflection and current anomalies.

ECM internal faults affecting the CAN transceiver circuit, though less common, can occur after electrical surges from jump-starting with improper polarity or welding on the machine without disconnecting batteries.

Damaged or aftermarket diagnostic cables left connected or improperly installed inline splitters for telematics systems that alter bus impedance.

How to Troubleshoot and Fix Code 45662 SPN651 FMI5

Step 1: Visual Inspection of Harness and Connectors Begin by thoroughly inspecting the main engine wiring harness from the ECM forward to the instrument cluster. On used XE750D excavators, pay special attention to the harness routing near the right-side hydraulic oil cooler mounting bracket—this is a known wear point. Look for abraded insulation, exposed copper, or signs of harness contact with sharp edges. Disconnect the ECM connector C1 (23-pin Deutsch connector) and inspect pins 6 and 14 (CAN High and CAN Low)—check for green corrosion, bent pins, or moisture inside the connector boot. Clean contacts with electrical contact cleaner and apply dielectric grease before reconnection.

Step 2: Measure CAN Bus Resistance Using a digital multimeter (DMM) set to ohms, disconnect all power to the machine and measure resistance between CAN High and CAN Low terminals at the diagnostic port (9-pin Deutsch connector located near the operator's right foot). You should read approximately 60 ohms with all modules connected and powered down—this indicates both 120-ohm termination resistors are intact and parallel. A reading of 120 ohms suggests one terminator has failed; infinite resistance indicates an open circuit in the wiring. Check resistance again at the ECM connector to isolate whether the break is between ECM and diagnostic port or beyond.

Step 3: Check for Voltage and Ground Integrity Reconnect power and measure voltage on CAN High and CAN Low with engine key in the "ON" position (engine not running). Both wires should show approximately 2.5 volts DC relative to chassis ground—this is the recessive (idle) state voltage. Significant deviation (below 2.0V or above 3.0V) indicates a short to power, short to ground, or failed ECM driver circuit. Additionally, verify the ECM ground circuit (pins 1 and 12 on C1 connector) shows less than 0.1 ohms resistance to a known good chassis ground point—poor grounding is common in used machines where mounting bolts have corroded.

Step 4: Test Diagnostic Port and Telematics Devices Disconnect any aftermarket telematics units, fleet management devices, or diagnostic adapters that may be spliced into the CAN bus. These devices can introduce impedance mismatches or draw excessive current. After removal, clear codes and test-run the machine. If the fault disappears, the aftermarket device requires proper CAN bus isolation or replacement with a compatible unit designed for J1939 networks.

Step 5: Replace Damaged Components If physical damage is found in the harness, repair or replace the affected section using appropriate gauge wire (typically 18 AWG twisted shielded pair for CAN applications). Ensure repairs use heat-shrink solder connectors rather than crimp splices, and maintain the twisted-pair configuration to preserve signal integrity. If the ECM is suspected after all wiring checks pass, replacement requires programming with XCMG's XC-Tech diagnostic software—ensure the replacement ECM matches the machine serial number range and software version to avoid compatibility issues.

---

Disclaimer: This guide provides general troubleshooting information for educational purposes. Always consult the official XCMG service manual for your specific machine serial number and software version. If you lack experience with high-voltage systems or CAN bus diagnostics, seek assistance from a certified XCMG technician or qualified heavy equipment electrician to prevent further damage or safety hazards.