What is Hyundai R505LC-7 Fault Code 108-2?

Fault Code 108-2 on the Hyundai R505LC-7 excavator indicates an abnormal voltage signal from the atmospheric pressure sensor circuit, specifically a "data erratic/intermittent/incorrect" condition. This code is triggered when the Electronic Control Module (ECM) detects inconsistent or out-of-range readings from the barometric pressure sensor, which measures ambient air pressure to optimize engine fuel injection and air-fuel ratios.

The atmospheric pressure sensor plays a critical role in the R505LC-7's engine performance, particularly at varying altitudes. The ECM uses this data to compensate for changes in air density, ensuring proper combustion efficiency and power output. When Code 108-2 appears, the engine management system may revert to default atmospheric pressure values, potentially causing reduced performance and increased fuel consumption.

Common Symptoms

• Check Engine Light (CEL) or malfunction indicator illuminated on the instrument panel
• Noticeable loss of engine power or sluggish throttle response, especially at higher elevations
• Rough idling or irregular engine operation during startup or warm-up
• Increased black smoke from the exhaust due to improper fuel-air mixture calibration
• Intermittent activation and deactivation of the fault code, particularly during temperature changes or machine vibration

Potential Causes

The most common technical causes for Code 108-2 on used R505LC-7 excavators include:

• Faulty atmospheric pressure sensor due to internal component degradation or contamination
• Corroded or loose electrical connectors at the sensor harness (common in machines exposed to moisture or harsh environments)
• Damaged wiring harness with chafed insulation, particularly where the harness routes near moving components or sharp edges
• Poor ground connection at the sensor mounting point or ECM ground terminals
• ECM software glitches or corrupted calibration data (less common but possible in older units)
• Intermittent short circuits caused by water intrusion into the sensor connector

How to Troubleshoot and Fix Code 108-2

Step 1: Visual Inspection Begin by locating the atmospheric pressure sensor, typically mounted on or near the ECM housing. Inspect the sensor connector for corrosion, bent pins, moisture, or loose connections. On used excavators, check the wiring harness routing for wear points where cables may rub against metal brackets or the engine block.

Step 2: Electrical Testing Using a digital multimeter, check the sensor's power supply voltage (typically 5V reference from the ECM) and ground continuity. Measure the sensor's output signal voltage—it should read approximately 3.5-4.5V at sea level. Compare readings with Hyundai's specification chart for different altitudes. Check for resistance values between sensor terminals per the service manual.

Step 3: Signal Verification and Component Replacement Connect Hyundai Hi-MATE diagnostic software or compatible scan tool to monitor live sensor data. Observe for erratic voltage fluctuations or frozen readings. If electrical values test correctly but the code persists, replace the atmospheric pressure sensor with a genuine or OEM-equivalent part. Clear codes and perform a test cycle under load.

Step 4: Harness and Ground Verification For intermittent codes on used machines, thoroughly inspect all harness retention clips and grommets. Apply dielectric grease to connectors after cleaning. Verify ECM ground straps are tight and corrosion-free.

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Disclaimer: This guide provides general troubleshooting information. Always consult the Hyundai R505LC-7 service manual and consider professional diagnostic assistance for complex electrical issues or if you lack proper diagnostic equipment.