What is Sany SY245/265H Fault Code 106?

Fault Code 106 on the Sany SY245/265H excavator indicates an Intake Air Temperature (IAT) Sensor Circuit High Voltage condition. This diagnostic trouble code (DTC) is triggered when the Engine Control Module (ECM) detects an abnormally high voltage signal from the intake air temperature sensor, typically above 4.5-4.8 volts, which falls outside the manufacturer's programmed parameters.

The IAT sensor plays a critical role in the Mitsubishi Heavy Industries diesel engine's fuel management system. It monitors incoming air temperature and sends voltage signals to the ECM, which then calculates optimal fuel injection timing and air-fuel ratios. When Code 106 appears, the ECM cannot accurately determine intake air temperature, forcing the system into default "limp mode" parameters that can significantly reduce engine performance and fuel efficiency.

Common Symptoms

• Check Engine Light (CEL) or malfunction indicator lamp illuminated on the dashboard
• Noticeable loss of engine power or reduced throttle response, especially during heavy digging operations
• Hard starting in cold weather conditions due to improper fuel delivery calculations
• Rough idle or inconsistent engine RPM at low speeds
• Increased black smoke from the exhaust during acceleration or under load

Potential Causes

The most common technical reasons for Code 106 on used Sany excavators include:

• Open circuit in the IAT sensor wiring harness, often caused by wire breakage near movement points around the air intake manifold
• Failed IAT sensor with internal resistance breakdown (common after 5,000+ operating hours)
• Corroded or loose connector pins at the sensor plug, especially on machines operated in high-moisture or coastal environments
• Damaged wiring insulation due to heat exposure from the exhaust manifold or rubbing against engine components
• ECM internal fault (rare, but possible in high-hour machines with previous electrical issues)
• Intermittent short to battery voltage caused by chafed wires contacting positive voltage sources

How to Troubleshoot and Fix Code 106

Step 1: Visual Inspection Begin by locating the IAT sensor on the intake manifold (typically integrated into the Mass Air Flow sensor housing or positioned separately). Inspect the entire wiring harness from sensor to ECM for visible damage, burns, chafing, or corrosion. On used excavators, pay special attention to harness routing near moving components and heat sources.

Step 2: Electrical Testing Disconnect the IAT sensor connector and use a digital multimeter to measure resistance across the sensor terminals. At 68°F (20°C), resistance should read approximately 2,000-3,000 ohms (consult your service manual for exact specifications). If readings show infinite resistance (OL) or values outside range, replace the sensor.

Step 3: Circuit Voltage Check With the sensor disconnected and ignition on (engine off), measure voltage at the ECM-side harness connector. You should see approximately 5 volts reference voltage from the ECM. If voltage reads battery voltage (12-14V), there's a short to power in the harness requiring wire repair or replacement.

Step 4: Connector Service Clean all connector pins with electrical contact cleaner and inspect for bent pins or corrosion—a frequent issue in older machines. Apply dielectric grease to prevent future moisture intrusion.

Step 5: Clear Code and Test After repairs, clear the fault code using Sany diagnostic software or a compatible J1939 scan tool, then operate the machine through various load conditions to verify the repair.

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Disclaimer: This guide provides general troubleshooting information. Always consult the manufacturer's service manual and consider professional diagnostic assistance for complex electrical issues or if you're unfamiliar with high-voltage systems.