Komatsu PC750-7 Fault Code E113: Complete Diagnostic Guide

What is Komatsu PC750-7 Fault Code E113?

Fault Code E113 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 E113 is active, operators typically experience:

• Warning light illumination on the instrument cluster, specifically the engine oil pressure lamp (red)
• Audible alarm sounding continuously or intermittently during operation
• Engine derate or automatic shutdown in severe cases, limiting machine performance to protect internal components
• Erratic oil pressure gauge readings or gauge showing zero pressure despite engine running normally
• Reduced hydraulic response if the ECM enters protective mode and limits engine RPM

Potential Causes

The most common technical causes for E113 on used PC750-7 excavators include:

• Failed oil pressure sensor due to internal diaphragm deterioration or contamination from debris in aged oil
• Damaged wiring harness between the sensor and ECM, particularly at known rub points near the engine mount brackets
• Corroded or loose electrical connectors at the sensor terminal, common in machines with high operating hours in wet environments
• Actual low oil pressure caused by worn oil pump, clogged oil filter, or excessive bearing clearances
• ECM calibration issues or internal ECM faults affecting the pressure monitoring circuit
• Contaminated engine oil with incorrect viscosity affecting pressure readings

How to Troubleshoot and Fix Code E113

Step 1: Visual Inspection and Oil Level Verification Begin by checking actual engine oil level using the dipstick. Verify oil condition for contamination or incorrect viscosity. Inspect the oil pressure sensor (located on the left side of the engine block) for physical damage, oil leaks, or loose mounting. On used excavators, carefully examine the sensor wiring harness for abrasion, particularly where it routes near moving components or sharp edges.

Step 2: Electrical Circuit Testing Using a digital multimeter, disconnect the oil pressure sensor connector and measure resistance across the sensor terminals. Compare readings against Komatsu specifications (typically 50-150 ohms at 20°C, varying with pressure). Check for supply voltage at the harness connector (should read approximately 5V with key on, engine off). Inspect connector pins for corrosion or bent terminals, cleaning with electrical contact cleaner if necessary.

Step 3: Live Pressure Verification Install a mechanical oil pressure gauge at the sensor port to verify actual engine oil pressure during operation. At normal operating temperature, idle pressure should exceed 50 psi, with running pressure at 1,800 RPM reaching 70-85 psi. If mechanical readings are normal but the code persists, replace the pressure sensor. If actual pressure is low, investigate the lubrication system: replace the oil filter, inspect the oil pump drive gear, and consider bearing clearance inspection on high-hour machines.

Step 4: Advanced Diagnostics Connect Komatsu KOMTRAX or compatible diagnostic software to monitor live sensor data and verify ECM response. Clear the fault code and perform a test cycle. For persistent codes with good pressure and sensor readings, inspect ECM ground connections and consider ECM reprogramming or replacement.

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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 from certified Komatsu technicians for complex repairs, especially those involving engine disassembly or ECM replacement.