Komatsu PC750-7 Fault Code E117: Complete Diagnostic Guide

What is Komatsu PC750-7 Fault Code E117?

Fault Code E117 on the Komatsu PC750-7 indicates a malfunction in the engine oil pressure sensor circuit or abnormally low engine oil pressure detection. This code is triggered when the Engine Control Module (ECM) detects voltage readings outside the normal operating range from the oil pressure sensor, or when actual oil pressure falls below the manufacturer's specified threshold during operation.

The oil pressure monitoring system is critical for the PC750-7's SAA6D140E-5 engine, as it protects against catastrophic bearing failure and ensures proper lubrication of high-stress components. When this code activates, the ECM may initiate protective measures to prevent engine damage, making immediate diagnosis essential for machine longevity.

Common Symptoms

When Code E117 is active, operators typically experience:

• Warning light illumination on the instrument cluster, specifically the engine oil pressure lamp (red)
• Engine power derate or automatic shutdown in severe cases to prevent damage
• Audible alarm from the cab monitoring system
• Intermittent code logging that may appear during cold starts or high-load operations
• Erratic oil pressure gauge readings or gauge showing zero pressure despite engine running normally

Potential Causes

The most common technical causes for E117 on used PC750-7 excavators include:

• Failed oil pressure sensor (Komatsu part 6732-81-3140) due to internal diaphragm deterioration
• Damaged wiring harness between the sensor and ECM, particularly at the engine valley routing point where heat and vibration cause insulation breakdown
• Corroded or loose connector pins at the sensor plug (3-pin connector), common in machines with high operating hours
• Low actual engine oil pressure caused by worn oil pump, clogged oil filter, or bearing clearance issues
• ECM internal fault in the sensor input circuit (rare but possible in high-hour machines)
• Contaminated engine oil causing sensor port blockage

How to Troubleshoot and Fix Code E117

Step 1: Visual Inspection Begin by locating the oil pressure sensor on the left side of the engine block near the oil filter housing. Inspect the wiring harness for obvious damage, chafing, or oil contamination. Check the connector for corrosion, bent pins, or moisture intrusion—common issues on used excavators operating in harsh environments.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure resistance across the sensor terminals. The sensor should read approximately 50-150 ohms at room temperature (consult service manual for exact specifications). Check supply voltage at the harness connector with ignition on—should read approximately 5 volts from the ECM. Measure ground continuity to ensure less than 1 ohm resistance.

Step 3: Mechanical Verification Install a mechanical oil pressure gauge at the sensor port to verify actual oil pressure. At operating temperature and idle, pressure should be minimum 50 psi (3.5 kg/cm²). If mechanical pressure is adequate but the code persists, replace the sensor. If pressure is low, investigate the lubrication system: check oil level, inspect the oil pump, and verify filter condition.

Step 4: Harness and Connector Repair For used excavators, carefully inspect the harness routing through the engine valley where heat and vibration commonly cause wire fatigue. Apply dielectric grease to connector pins and ensure proper sealing. Replace any damaged sections with OEM-spec wire and heat-shrink connectors.

Disclaimer: This guide provides general diagnostic procedures. Always consult the official Komatsu service manual for your specific machine serial number. Complex repairs should be performed by certified technicians with proper diagnostic equipment.