What is XCMG XE750D Fault Code 45752 SPN654 FMI5?

Fault Code 45752 (SPN 654 FMI 5) indicates an abnormally low current or open circuit detected in the Idle Validation Switch circuit. This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) detects that the electrical current flowing through the idle validation switch is below the expected threshold or the circuit is completely open.

SPN 654 specifically refers to the Idle Validation Switch, a component that confirms the engine's idle position and throttle status. FMI 5 designates a current below normal or an open circuit condition. For the XCMG XE750D excavator, this fault can compromise engine idle control, leading to erratic performance and potential fuel efficiency issues. The ECM relies on this signal to properly manage engine speed during idle and transition phases, making this code critical for smooth operation.

Common Symptoms

• Check Engine Light (CEL) or malfunction indicator lamp illuminated on the operator display panel
• Erratic or unstable idle speed, with the engine surging or hunting for proper RPM
• Engine stalling when returning to idle after operation or during warm-up cycles
• Poor throttle response or delayed acceleration when moving from idle to working speed
• Increased fuel consumption due to improper idle management and ECM compensation strategies

Potential Causes

The most common technical reasons for Code 45752 on used XCMG XE750D excavators include:

• Open or broken wiring in the idle validation switch harness, particularly at flex points near the engine mount or cab pivot areas
• Corroded or damaged electrical connectors at the switch or ECM interface, common in machines exposed to moisture or extreme conditions
• Failed idle validation switch due to internal component wear or mechanical damage
• Chafed wiring harness rubbing against frame components or hydraulic lines—a known wear point on older XE750D models
• Poor ground connection at the switch mounting point or ECM ground strap
• ECM internal circuit failure (rare, but possible in high-hour machines)

How to Troubleshoot and Fix Code 45752 SPN654 FMI5

Step 1: Visual Inspection Begin with a thorough visual examination of the idle validation switch and its wiring harness. On used excavators, pay special attention to areas where the harness routes near moving components or sharp edges. Look for obvious signs of wire chafing, cuts, or connector corrosion. Inspect the switch mounting bracket for looseness that could cause intermittent connections.

Step 2: Electrical Testing Using a digital multimeter (DMM), check for continuity in the idle validation switch circuit. Disconnect the switch connector and measure resistance across the switch terminals according to XCMG specifications (typically 100-300 ohms when closed). Test the harness for continuity from the switch connector back to the ECM pins. Check for proper supply voltage (usually 5V reference) from the ECM with the key on, engine off.

Step 3: Circuit and Ground Verification Verify the ground circuit integrity by measuring resistance between the switch ground terminal and a known good chassis ground (should be less than 1 ohm). Inspect the ECM harness connector for bent pins, corrosion, or moisture intrusion—common issues in machines with high operating hours.

Step 4: Component Replacement and Verification If testing reveals a faulty switch, replace it with an OEM or equivalent quality component. For used machinery, always replace the connector pigtail if any corrosion is present, as this prevents repeat failures. After replacement, clear the fault code using XCMG diagnostic software or a compatible J1939 scan tool, then perform a road test to verify proper idle operation and confirm the code does not return.

Disclaimer: This guide provides general troubleshooting information. Always consult the official XCMG service manual for your specific machine serial number and software version. For complex electrical diagnostics or ECM programming, professional consultation with a certified XCMG technician is recommended.