Komatsu PC450LC-6 Fault Code E318: Complete Diagnostic Guide

What is Komatsu PC450LC-6 Fault Code E318?

Fault Code E318 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 experiences electrical faults or actual oil pressure drops below threshold values (typically below 50 kPa at idle), the ECM triggers E318. 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 E318 is active, operators typically experience:

• Engine warning light illuminated on the monitor panel, 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 abnormally low pressure
• Increased engine noise such as knocking or ticking sounds from valve train or main bearings
• Hesitation or power loss during high-load operations like digging or lifting

Potential Causes

The most common technical causes for E318 on used PC450LC-6 excavators include:

• Failed oil pressure sensor due to internal diaphragm deterioration or contamination (common after 8,000+ hours)
• Damaged wiring harness at sensor connector, particularly where harness routes near engine mounts (known rub point)
• Corroded or loose electrical connections at the sensor or ECM terminals
• Actual low oil pressure caused by worn oil pump, clogged oil filter, or excessive bearing clearances
• Low engine oil level or use of incorrect viscosity oil for operating conditions
• ECM calibration issues or internal ECM fault (rare but possible in high-hour machines)

How to Troubleshoot and Fix Code E318

Step 1: Visual Inspection and Basic Checks

Begin by checking engine oil level using the dipstick—ensure oil is at proper level and not contaminated with coolant or fuel. Inspect the oil pressure sensor (located on the engine block's left side near the oil filter housing) for physical damage, oil leaks, or loose mounting. Examine the sensor harness for chafing, cuts, or heat damage, especially where it passes near the turbocharger and exhaust manifold.

Step 2: Electrical Circuit Testing

Using a digital multimeter, disconnect the oil pressure sensor connector and measure resistance across sensor terminals. Typical resistance should be 50-150 ohms at room temperature (consult service manual for exact specifications). Check for supply voltage at the harness connector—should read approximately 5 volts with ignition on. Measure ground continuity between sensor ground pin and chassis ground (should be less than 1 ohm). On used excavators, corrosion inside connectors is extremely common; clean terminals with electrical contact cleaner and apply dielectric grease.

Step 3: Mechanical Pressure Verification

If electrical tests pass, install a mechanical oil pressure gauge in place of the sensor to verify actual oil pressure. Start the engine and observe readings: should show 300-450 kPa at operating temperature and rated RPM. Low mechanical pressure indicates internal engine wear—check oil pump condition, main bearing clearances, and oil filter bypass valve operation.

Step 4: Component Replacement and Verification

Replace the oil pressure sensor if electrical values are out of specification or mechanical pressure tests normal. Use genuine Komatsu parts (part number 7861-93-1650) to ensure proper ECM communication. After replacement, clear fault codes using Komatsu diagnostic software (KOMTRAX) or compatible scan tool, then operate machine under load while monitoring for code recurrence.

Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu PC450LC-6 service manual and consider professional assessment by certified technicians for complex repairs, especially on high-hour used equipment where multiple underlying issues may exist.