Sumitomo SH300-6 Fault Code 118: Complete Diagnostic Guide

What is Sumitomo SH300-6 Fault Code 118?

Fault Code 118 on the Sumitomo SH300-6 excavator indicates a malfunction in the engine oil pressure sensor circuit or abnormally low engine oil pressure detection. This code is triggered when the Electronic Control Module (ECM) receives signals outside the expected voltage range from the oil pressure sensor, or when actual oil pressure falls below the manufacturer's minimum threshold during operation.

This fault is critical for the SH300-6 because insufficient oil pressure can lead to catastrophic engine damage. The Isuzu engine powering this excavator relies on precise oil pressure monitoring to protect bearings, camshafts, and other lubricated components. When Code 118 activates, the ECM may initiate engine derate or automatic shutdown to prevent internal damage.

Common Symptoms

When Code 118 is active on your SH300-6, you may experience:

• Oil pressure warning light illuminated on the instrument cluster (typically red)
• Engine power reduction or automatic derate to idle speed
• Audible warning alarm sounding in the operator cabin
• Engine shutdown during operation, particularly under load or at operating temperature
• Rough idle or hesitation if oil pressure is borderline but not critically low

Potential Causes

The most common technical causes for Code 118 on used SH300-6 excavators include:

• Faulty oil pressure sensor – sensor degradation is common after 5,000+ hours
• Damaged or corroded wiring harness at the sensor connector (known wear point near engine block)
• Low engine oil level due to leaks or consumption in high-hour machines
• Worn oil pump or pressure relief valve stuck open (typical in excavators exceeding 8,000 hours)
• Clogged oil filter restricting flow and reducing system pressure
• ECM calibration issues or internal ECM fault (less common)
• Corroded ground connections affecting sensor signal accuracy

How to Troubleshoot and Fix Code 118

Step 1: Verify Actual Oil Pressure Install a mechanical oil pressure gauge at the engine test port. Start the engine and compare actual pressure against specifications (typically 30-45 PSI at idle, 50-70 PSI at rated RPM). This confirms whether the issue is actual low pressure or a sensor/electrical fault.

Step 2: Inspect the Oil Pressure Sensor and Wiring Locate the oil pressure sensor on the engine block (driver's side, near oil filter housing on SH300-6). Inspect the connector for corrosion, oil contamination, or bent pins. Check the wiring harness for rubbing damage where it contacts the engine—this is a known failure point on used Sumitomo excavators. Use a digital multimeter to test sensor resistance (typically 50-250 ohms when disconnected) and reference voltage (should be 5V from ECM).

Step 3: Check Oil System Components If actual pressure is low, inspect engine oil level and condition. Replace the oil filter if overdue. For high-hour machines, remove the oil pan and inspect the oil pump pickup screen for debris. Test the pressure relief valve operation—these often stick open in used equipment.

Step 4: Clear Codes and Test After repairs, use Sumitomo diagnostic software or a compatible J1939 scan tool to clear fault codes. Operate the excavator under load while monitoring live oil pressure data to confirm the fix.

Disclaimer: This guide provides general troubleshooting information. Always consult the official Sumitomo service manual and consider professional diagnosis for complex engine issues, especially on used equipment where multiple underlying problems may exist.