What is XCMG XE750D Fault Code 3528-4 SPN108 FMI4?

Fault Code 3528-4 (SPN 108 FMI 4) indicates a voltage below normal or shorted to ground condition in the barometric pressure sensor circuit. This code is triggered when the Engine Control Module (ECM) detects an electrical signal from the barometric pressure sensor that falls outside the acceptable voltage range, specifically reading lower than the predetermined threshold.

The barometric pressure sensor on the XCMG XE750D excavator plays a critical role in engine performance optimization. This sensor measures atmospheric pressure and sends data to the ECM, which uses this information to adjust fuel injection timing, air-fuel ratios, and turbocharger boost pressure. When this sensor circuit malfunctions, the engine cannot properly compensate for altitude changes or atmospheric conditions, directly impacting fuel efficiency, power output, and emissions compliance. For a large excavator like the XE750D operating in varying environments, accurate barometric readings are essential for maintaining optimal hydraulic system performance and preventing premature engine wear.

Common Symptoms

• Check Engine Light or malfunction indicator lamp illuminated on the instrument cluster
• Noticeable loss of engine power, particularly at higher altitudes or during demanding hydraulic operations
• Rough idle or inconsistent engine RPM, especially during warm-up cycles
• Increased black smoke from exhaust due to improper fuel-to-air mixture calculations
• Reduced hydraulic response time or weakened digging force as the ECM enters a derated operating mode

Potential Causes

Wiring harness damage is the most common culprit in used XCMG excavators, particularly where the sensor harness routes near the engine block or exhaust components. Years of vibration create rub points that wear through insulation, causing intermittent shorts to ground.

Corroded or loose connector pins at the barometric pressure sensor connection point allow moisture intrusion, especially in machines operating in humid or coastal environments.

Failed barometric pressure sensor due to internal component degradation, though less common than wiring issues in used equipment.

ECM grounding problems or corroded chassis ground connections can create voltage reference issues that trigger this fault.

Previous repair attempts using incorrect wire gauge or improper splice techniques may create high-resistance connections.

How to Troubleshoot and Fix Code 3528-4 SPN108 FMI4

Step 1: Visual Inspection Begin by locating the barometric pressure sensor, typically mounted on the engine intake manifold or ECM housing. Thoroughly inspect the entire wiring harness from sensor to ECM for visible damage, chafing, or burn marks. Pay special attention to areas where harnesses contact metal edges or pass near hot exhaust components—common wear points on used XE750D excavators.

Step 2: Connector and Pin Testing Disconnect the barometric pressure sensor connector and inspect for corrosion, bent pins, or moisture. Clean contacts with electrical contact cleaner. Using a digital multimeter, check for continuity between sensor ground wire and chassis ground. Resistance should be less than 5 ohms. Also verify no continuity exists between signal wire and ground (infinite resistance when disconnected).

Step 3: Voltage Supply Check With ignition on and sensor disconnected, measure voltage at the connector's supply pin (consult XCMG wiring diagram for specific pin identification). You should read approximately 5 volts. If voltage is absent or incorrect, trace wiring back to ECM checking for breaks or shorts.

Step 4: Sensor Resistance Testing Measure resistance across the sensor terminals per manufacturer specifications (typically 3,500-4,500 ohms at sea level). Replace sensor if readings fall outside this range.

Step 5: Repair and Verification For used excavators, replace entire harness sections rather than splicing if damage is found—this prevents future failures. After repairs, clear codes using diagnostic software (XCMG ADAPT or compatible J1939 scan tool) and perform a test cycle under load to verify repair.

---

Disclaimer: This guide provides general troubleshooting information. Always consult the official XCMG service manual for your specific machine serial number and consider professional diagnostic services for complex electrical issues.