What is Hyundai R455LC-7 Fault Code 108-2?

Fault Code 108-2 on the Hyundai R455LC-7 excavator indicates a critical malfunction in the engine air intake temperature sensor circuit, specifically detecting an intermittent or out-of-range signal. This diagnostic trouble code (DTC) is generated when the Engine Control Module (ECM) receives voltage readings from the Intake Air Temperature (IAT) sensor that fall outside the manufacturer's specified parameters or fluctuate abnormally during operation.

The IAT sensor plays a vital role in the R455LC-7's engine management system by monitoring incoming air temperature and sending data to the ECM. This information directly influences fuel injection timing, air-fuel ratio calculations, and combustion efficiency. When Code 108-2 triggers, the ECM cannot accurately optimize engine performance, potentially leading to increased fuel consumption, reduced power output, and elevated emissions—critical concerns for operators managing fuel costs on used excavators.

Common Symptoms

When Code 108-2 is active on your Hyundai R455LC-7, you may experience:

• Check Engine Light illuminated on the instrument cluster with possible reduced engine power mode
• Hard starting conditions, particularly in cold weather when accurate air temperature readings are most critical
• Rough idling or engine hunting (RPM fluctuations) during warm-up cycles
• Black smoke from the exhaust due to improper air-fuel mixture calibration
• Decreased throttle response and noticeable loss of hydraulic system performance under load

Potential Causes

The most common technical causes for Code 108-2 on used R455LC-7 excavators include:

• Corroded or loose connector at the IAT sensor—extremely common on machines operating in high-moisture or marine environments
• Damaged sensor wiring harness from rubbing against the air intake ductwork or engine components (known wear point on this model)
• Failed IAT sensor due to age-related internal component degradation or thermal stress
• Contaminated sensor element from oil mist, dirt, or carbon buildup in the intake system
• ECM voltage supply issues or poor ground connections affecting sensor circuit integrity
• Aftermarket air filter modifications creating airflow disruptions that affect sensor readings

How to Troubleshoot and Fix Code 108-2

Step 1: Visual Inspection and Connector Assessment Begin by locating the IAT sensor on the air intake manifold. Disconnect the electrical connector and thoroughly inspect both the sensor pins and harness connector for corrosion, bent terminals, or moisture intrusion. On used excavators, these connectors often accumulate conductive dirt that creates false readings. Clean with electrical contact cleaner and apply dielectric grease before reconnecting.

Step 2: Sensor Resistance Testing Using a digital multimeter (DMM), measure the resistance across the IAT sensor terminals at ambient temperature. Compare your reading against Hyundai's specification chart (typically 2,000-3,000 ohms at 20°C/68°F). The resistance should decrease smoothly as temperature increases. Erratic or out-of-spec readings confirm sensor failure.

Step 3: Wiring Harness Continuity Check With the sensor disconnected, test for continuity between the sensor connector and the ECM harness connector (consult service manual for pin locations). Check for short circuits to ground on the signal wire. On used R455LC-7 excavators, inspect the harness routing near the turbocharger and exhaust manifold—heat damage and harness chafing are common failure points.

Step 4: Voltage Supply Verification With ignition on and sensor disconnected, measure voltage at the harness connector. You should see approximately 5 volts reference voltage from the ECM. Significantly lower voltage indicates ECM issues or wiring problems. Also verify proper ground continuity (less than 0.5 ohms resistance to chassis ground).

Step 5: Component Replacement and Code Clearing If testing confirms sensor failure, replace with an OEM Hyundai IAT sensor for best reliability. Aftermarket sensors often have different resistance curves causing calibration issues. After replacement, clear the code using Hi-SCANPro diagnostic software or equivalent Hyundai-compatible scan tool, then perform a test run to verify the repair.

Disclaimer: This guide provides general troubleshooting information for the Hyundai R455LC-7. Always consult the manufacturer's official service manual and consider seeking assistance from certified Hyundai heavy equipment technicians for complex electrical diagnostics, especially when dealing with ECM programming or calibration issues.