What is Sany SY245/265H Fault Code 107?

Fault Code 107 on the Sany SY245/265H excavator indicates an Intake Air Temperature (IAT) Sensor Circuit High Voltage condition in the Mitsubishi Heavy Industries diesel engine's Electronic Control Module (ECM). This diagnostic trouble code triggers when the ECM detects an abnormally high voltage signal (typically above 4.5-4.8 volts) from the intake air temperature sensor, which monitors the temperature of air entering the combustion system.

The IAT sensor plays a critical role in engine performance by providing data that allows the ECM to adjust fuel injection timing and air-fuel ratios for optimal combustion. When this sensor circuit reports high voltage, the ECM cannot accurately calculate air density, leading to improper fuel delivery, reduced power output, and increased emissions. For used excavators operating in demanding conditions, this fault can significantly impact productivity and fuel efficiency.

Common Symptoms

• Check Engine Light or malfunction indicator lamp illuminated on the dashboard
• Noticeable loss of engine power or reduced throttle response, especially under load
• Hard starting or rough idle conditions, particularly in cold weather
• Black smoke from the exhaust due to rich fuel mixture from incorrect air density calculations
• Engine may enter derate mode, limiting maximum RPM to protect components

Potential Causes

The high voltage reading for Code 107 typically results from circuit interruptions rather than sensor overheating. Common causes in used Sany excavators include:

• Open circuit in the IAT sensor wiring harness due to wire breakage or connector separation
• Corroded or damaged connector pins at the sensor or ECM connection points (common in machines exposed to moisture)
• Failed IAT sensor with internal open circuit, preventing proper ground signal
• Wiring harness chafing at known rub points near the air intake manifold or engine valley
• ECM internal fault (rare, but possible in high-hour machines with electrical system damage)

How to Troubleshoot and Fix Code 107

Step 1: Visual Inspection Begin with a thorough inspection of the IAT sensor located in the intake manifold. Check the sensor connector for corrosion, bent pins, moisture intrusion, or loose connections. On used excavators, examine the wiring harness for signs of rubbing, cracking, or damage along its entire length from sensor to ECM.

Step 2: Sensor and Circuit Testing Using a digital multimeter, measure the resistance of the IAT sensor with the connector disconnected. At 68°F (20°C), resistance should typically read between 2,000-3,000 ohms (consult Mitsubishi specifications). Check for continuity in the signal and ground wires from the sensor connector to the ECM harness. High resistance or open circuits indicate wiring problems.

Step 3: Voltage Testing With ignition on and sensor disconnected, measure voltage at the ECM side of the harness connector. You should see approximately 5 volts on the signal wire. If voltage is present, the ECM and power supply are functioning correctly, pointing to sensor or ground circuit failure.

Step 4: Component Replacement If testing confirms sensor failure, replace the IAT sensor with an OEM or quality aftermarket unit. For used machines, always apply dielectric grease to connector pins to prevent future corrosion. If wiring damage is found, repair using proper gauge wire and heat-shrink connections, ensuring the harness is secured away from heat sources and moving components.

Step 5: Clear Code and Verify After repairs, clear the fault code using Mitsubishi diagnostic software or a compatible scan tool. Run the engine through various operating temperatures and loads to confirm the code does not return.

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Disclaimer: This guide provides general diagnostic information for Fault Code 107. Complex electrical issues or ECM programming may require consultation with a certified Sany dealer or qualified diesel technician with access to manufacturer-specific diagnostic equipment.