What is Hyundai R335LC-9T Fault Code 108-2?

Fault Code 108-2 on the Hyundai R335LC-9T excavator indicates an intermittent or abnormal signal from the Atmospheric Pressure Sensor (APS) circuit. This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) detects voltage readings outside the expected range or an unstable signal pattern from the sensor responsible for monitoring ambient air pressure.

The Atmospheric Pressure Sensor plays a critical role in the R335LC-9T's engine management system. It provides the ECM with real-time barometric pressure data, which directly affects fuel injection timing, air-fuel ratio calculations, and turbocharger boost control. On this Tier 4 Final compliant machine, accurate atmospheric pressure readings are essential for maintaining emissions compliance and optimal engine performance, especially when operating at varying altitudes or in different weather conditions.

Common Symptoms

When fault code 108-2 is active on your Hyundai excavator, operators typically experience:

• Check Engine Light (CEL) illuminated on the instrument cluster with reduced engine power
• Noticeable loss of hydraulic response or sluggish boom/arm movements during operation
• Engine derate mode activated, limiting RPM to approximately 1500-1800 range
• Difficulty starting in cold weather or at high elevations above 3,000 feet
• Black smoke from the exhaust under load due to improper fuel mapping

Potential Causes

The most common technical reasons for code 108-2 appearing on used R335LC-9T excavators include:

• Corroded or moisture-contaminated connector at the atmospheric pressure sensor (located near the ECM housing)
• Damaged sensor wiring harness due to vibration wear or rubbing against the engine valve cover—a known issue on machines with 4,000+ operating hours
• Failed Atmospheric Pressure Sensor itself, particularly on machines operated in dusty or marine environments
• Intermittent ground connection at the ECM mounting bracket causing voltage fluctuations
• Aftermarket ECM reflash or software corruption affecting sensor calibration parameters

How to Troubleshoot and Fix Code 108-2

Step 1: Visual Inspection and Connector Check Begin by locating the Atmospheric Pressure Sensor mounted on or near the ECM housing on the right side of the engine compartment. Disconnect the sensor's electrical connector and inspect for corrosion, bent pins, or moisture intrusion. Clean contacts with electrical contact cleaner and apply dielectric grease before reconnecting. On used excavators, this simple fix resolves the issue approximately 40% of the time.

Step 2: Sensor Signal Testing Using a digital multimeter (DMM), backprobe the sensor connector while connected. Measure the supply voltage (should read 4.8-5.2 VDC) on the reference pin and verify the signal voltage output (typically 3.5-4.5 VDC at sea level). Compare readings against Hyundai's Hi-Mate diagnostic software specifications. Fluctuating voltage or readings outside this range indicate sensor failure.

Step 3: Wiring Harness Continuity Test Disconnect both the sensor and the ECM connector. Check for continuity between corresponding pins and measure resistance (should be less than 5 ohms). Inspect the harness routing along the fuel rail and valve cover—these are common rub points on the R335LC-9T where insulation wear causes intermittent shorts to ground.

Step 4: Sensor Replacement and Calibration If testing confirms sensor failure, replace with a genuine Hyundai atmospheric pressure sensor (part number varies by production year). After installation, clear codes using Hi-Mate or compatible diagnostic software and perform a sensor calibration procedure at current altitude. Test operation under load for at least 30 minutes to confirm repair.

For used excavators specifically: Always inspect the engine compartment insulation and harness protective loom condition, as deterioration accelerates sensor-related faults. Check maintenance records for previous electrical issues that might indicate systemic wiring problems.

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Disclaimer: This guide provides general troubleshooting information for reference purposes. Diagnostic procedures should be performed by qualified diesel technicians using proper safety equipment and manufacturer-approved tools. Always consult the official Hyundai service manual and consider professional diagnosis for complex electrical issues.