What is Komatsu PC100-6 Fault Code E106?

Fault Code E106 indicates a malfunction in the engine oil pressure sensor circuit or abnormally low oil pressure detection in the Komatsu PC100-6 excavator. This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) detects voltage readings outside the normal operating range from the oil pressure sensor, or when actual oil pressure falls below critical thresholds during engine operation.

The oil pressure monitoring system is critical for the PC100-6's SAA4D95LE engine protection. When this code activates, it directly impacts the engine's ability to maintain proper lubrication, potentially leading to catastrophic engine failure if ignored. The ECM continuously monitors oil pressure to prevent damage to bearings, camshafts, and crankshafts.

Common Symptoms

• Oil pressure warning lamp illuminates on the instrument panel continuously or intermittently
• Engine derate mode activation, limiting RPM to approximately 1,500 or causing automatic shutdown
• Abnormal engine noise such as knocking or ticking from the valve train area, indicating insufficient lubrication
• Intermittent code triggering during cold starts or when the machine operates on slopes
• ECM logging multiple instances of the fault without immediate operator notification

Potential Causes

The E106 code on used PC100-6 excavators typically stems from age-related component degradation. The oil pressure sensor itself (part number 7861-93-1650) commonly fails due to internal diaphragm wear or contamination from metal particles in aged oil. Wiring harness issues are prevalent, particularly where the sensor harness routes near the engine block—heat and vibration cause insulation breakdown and short circuits.

Low actual oil pressure from worn oil pump components or excessive bearing clearances in high-hour machines triggers legitimate pressure drops. Clogged oil filters or using incorrect viscosity oil in older engines reduces flow rates. Corroded or loose connector terminals at the sensor or ECM create intermittent open circuits. ECM internal faults are rare but possible in machines exceeding 8,000 operating hours.

How to Troubleshoot and Fix Code E106

Step 1: Visual Inspection and Initial Checks Inspect the oil pressure sensor (located on the left side of the engine block near the oil filter) for physical damage, oil leaks, or corroded connectors. Check engine oil level and condition—contaminated or incorrect viscosity oil should be changed immediately. Examine the wiring harness for abrasion points, especially where it contacts the engine or frame.

Step 2: Electrical Testing Using a digital multimeter, measure sensor output voltage with the ignition on, engine off (should read approximately 0.5V). With engine running at operating temperature, voltage should increase to 2.5-4.5V depending on RPM. Test harness continuity from sensor to ECM pin (consult service manual for specific pin location). Resistance should be less than 5 ohms, and insulation resistance to ground should exceed 10 megohms.

Step 3: Pressure Verification and Component Replacement Install a mechanical oil pressure gauge at the sensor port to verify actual pressure (should be 285-427 kPa at rated RPM). If mechanical pressure is normal but code persists, replace the sensor. For used excavators, clean all connector terminals with electrical contact cleaner and apply dielectric grease before reconnection—corrosion is extremely common. If pressure reads low mechanically, inspect the oil pump and main bearings for wear.

Disclaimer: This guide provides general troubleshooting information. Always consult the official Komatsu service manual for your specific machine serial number. Complex electrical diagnostics or internal engine work should be performed by qualified technicians with appropriate diagnostic tools.