Komatsu PC450LC-6 Fault Code E108: Complete Diagnostic Guide

What is Komatsu PC450LC-6 Fault Code E108?

Fault Code E108 indicates a malfunction in the engine oil pressure sensor circuit or abnormally low engine oil pressure detected by the Engine Control Module (ECM). This code specifically relates to the oil pressure monitoring system that protects the Komatsu SAA6D125E-3 engine from catastrophic damage due to inadequate lubrication.

The oil pressure sensor sends continuous voltage signals to the ECM, which monitors whether oil pressure remains within safe operating parameters. When the sensor circuit shows an open/short condition or actual pressure drops below threshold values (typically below 50 kPa at idle), the ECM triggers E108. This is critical because insufficient oil pressure can lead to bearing failure, piston seizure, and complete engine destruction within minutes of operation.

Common Symptoms

When Code E108 is active, operators typically experience:

• Engine warning light illuminated on the instrument cluster, often accompanied by an audible alarm
• Automatic engine derate or shutdown in severe cases, limiting RPM to protect internal components
• Erratic oil pressure gauge readings or gauge showing zero pressure despite engine running normally
• Intermittent code activation during cold starts or when operating on steep slopes (common in used machines with worn sensors)
• Loss of power as the ECM enters protective mode to prevent engine damage

Potential Causes

The most common technical reasons for E108 on used PC450LC-6 excavators include:

• Failed oil pressure sensor (Komatsu part #6732-81-3140) due to internal diaphragm deterioration or contamination
• Damaged wiring harness between the sensor and ECM, particularly at the harness routing point near the engine mount where vibration causes wire chafing
• Corroded or loose electrical connectors at the sensor terminal, especially on machines with high hour counts or exposure to moisture
• Actual low oil pressure caused by worn oil pump, clogged oil filter, or bearing clearance issues in high-hour engines
• ECM internal fault in the sensor input circuit (rare but possible in machines with 10,000+ hours)

How to Troubleshoot and Fix Code E108

Step 1: Visual Inspection Begin by checking actual engine oil level and condition. Inspect the oil pressure sensor (located on the left side of the engine block near the oil filter housing) for oil leaks, physical damage, or loose mounting. Examine the sensor connector for corrosion, bent pins, or moisture intrusion—common issues in used excavators.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure resistance across the sensor terminals. A functional sensor typically shows 50-150 ohms at room temperature. Check harness continuity from the sensor connector to ECM pin (consult service manual for specific pin location). Measure supply voltage at the sensor connector with ignition on—should read approximately 5 volts from the ECM.

Step 3: Pressure Verification Install a mechanical oil pressure gauge in place of the sensor to verify actual oil pressure. At normal operating temperature, pressure should read 300-450 kPa at rated RPM. If mechanical pressure is adequate but the code persists, replace the oil pressure sensor. For used excavators, always inspect harness routing for wear points and apply protective sleeving before reassembly.

Step 4: Advanced Diagnostics If the issue persists after sensor replacement, use Komatsu KOMTRAX or compatible diagnostic software to monitor live sensor data and check for ECM-related faults. Inspect the oil pump and internal engine components if actual pressure remains low.

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Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu service manual for your specific machine serial number and consider professional assistance for complex repairs involving engine internals or ECM programming.