What is Hyundai R335LC-9T Fault Code 105-0?

Fault Code 105-0 on the Hyundai R335LC-9T 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 reading above 4.5-4.8 volts for more than 2 seconds.

The IAT sensor plays a critical role in the R335LC-9T's Scania DC13 engine management system by monitoring incoming air temperature. The ECM uses this data to calculate precise fuel injection timing and air-fuel ratios. When this sensor circuit fails high, the engine defaults to substitute values, resulting in compromised fuel efficiency, reduced power output, and potentially increased emissions. For used excavators operating in demanding conditions, this code can significantly impact jobsite productivity and fuel costs.

Common Symptoms

• Check Engine Light (CEL) or malfunction indicator lamp illuminated on the instrument cluster
• Reduced engine power or noticeable loss of throttle response, especially during cold starts
• Hard starting conditions in cold weather due to incorrect fuel mapping
• Black smoke from exhaust caused by overly rich fuel mixture from faulty sensor compensation
• Rough idle or irregular engine RPM fluctuations when machine is at operating temperature

Potential Causes

The most common technical failures triggering Code 105-0 on used R335LC-9T excavators include:

• Open circuit in IAT sensor wiring harness – particularly at flex points near the intake manifold where vibration causes wire fatigue
• Corroded or loose connector terminals at the sensor plug (common on machines with 5,000+ operating hours)
• Failed IAT sensor element – internal resistance breakdown causing permanently high voltage output
• Damaged ECM input circuit – rare but possible on machines exposed to water intrusion or electrical surges
• Chafed wiring at known rub points between the air intake assembly and engine block mounting brackets
• Poor ground connections at engine harness ground points, especially G101 and G103 locations

How to Troubleshoot and Fix Code 105-0

Step 1: Visual Inspection and Connector Check Begin by locating the IAT sensor on the intake air duct between the air filter and turbocharger inlet. Disconnect the 2-pin connector and inspect for corrosion, bent pins, or moisture intrusion. On used excavators, check the entire harness route for abrasion points where wiring contacts metal surfaces. Clean connectors with electrical contact cleaner and apply dielectric grease before reconnection.

Step 2: Sensor Resistance Testing Using a digital multimeter (DMM), measure the resistance across the IAT sensor terminals with the sensor disconnected. At 68°F (20°C), resistance should read approximately 2,300-2,700 ohms. At 176°F (80°C), it should drop to 270-330 ohms. Values outside this range indicate sensor failure requiring replacement (Hyundai part #11Q6-90900 or equivalent).

Step 3: Circuit Voltage Testing With ignition ON and sensor disconnected, measure voltage at the harness connector. The signal wire should show approximately 5.0 volts (reference voltage from ECM), while the ground wire should read near 0 volts. If signal wire shows battery voltage (12-24V) or no voltage, trace the wiring back to the ECM connector C138 checking for opens, shorts to power, or damaged insulation.

Step 4: Harness Continuity and Ground Verification Perform continuity tests between sensor connector and ECM pins (consult service manual for specific pin assignments). Resistance should be less than 5 ohms for signal and ground circuits. Pay special attention to chassis ground points – remove, clean with wire brush, and reinstall with anti-corrosive compound. Many used excavators develop ground issues causing multiple phantom codes.

Step 5: Clear Code and Monitor After repairs, clear the fault code using Hyundai Hi-MATE diagnostic software or compatible scan tool. Operate the machine through multiple temperature cycles and monitor for code recurrence. If Code 105-0 returns immediately, suspect ECM internal fault requiring advanced diagnostics.

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Disclaimer: This guide provides general troubleshooting information for experienced technicians. Always consult the official Hyundai R335LC-9T service manual and follow proper safety procedures. For complex electrical diagnostics or ECM-related issues, professional consultation with certified Hyundai heavy equipment technicians is recommended, especially for machines under warranty or service contracts.