Komatsu PC850SE-8R Fault Code S-13: Complete Diagnostic Guide

What is Komatsu PC850SE-8R Fault Code S-13?

Fault Code S-13 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 monitors the oil pressure sensor signal voltage and the actual oil pressure readings to ensure adequate lubrication throughout the engine's critical components.

In the Komatsu PC850SE-8R's SAA6D170E-5 engine, this fault directly affects the ECM's ability to protect the engine from catastrophic damage due to insufficient lubrication. The system continuously monitors oil pressure through a dedicated sensor mounted on the main oil gallery. When pressure falls below manufacturer specifications (typically below 50 kPa at idle or 200 kPa under load) or the sensor circuit shows irregular voltage, the ECM triggers S-13 and may initiate protective measures.

Common Symptoms

• Engine warning light illuminated on the operator display panel with audible alarm
• Engine derate mode activated, limiting maximum RPM to approximately 1,200-1,500 to prevent damage
• Visible low oil pressure warning message on the monitor screen
• Automatic engine shutdown in severe cases (depending on ECM programming)
• Unusual engine noise such as valve train ticking or knocking if actual oil pressure is critically low

Potential Causes

Sensor-Related Issues:

• Failed or degraded oil pressure sensor (common in high-hour machines beyond 8,000 hours)
• Corroded or damaged sensor connector pins due to environmental exposure
• Wiring harness chafing near the engine block mounting points (known wear point on PC850 models)

Mechanical Issues:

• Genuinely low oil pressure from worn oil pump or excessive bearing clearances
• Clogged oil filter restricting flow (especially in used excavators with inconsistent maintenance)
• Low engine oil level or contaminated oil reducing viscosity
• Blocked oil pressure sensor port from sludge accumulation

How to Troubleshoot and Fix Code S-13

Step 1: Initial Verification Connect Komatsu diagnostic software (KOMTRAX Plus or equivalent) to verify active fault codes and monitor real-time oil pressure readings. Check physical oil level using the dipstick and inspect oil condition for contamination or metallic particles.

Step 2: Sensor Circuit Testing Locate the oil pressure sensor on the engine block's left side near the oil filter housing. Disconnect the sensor connector and inspect for corrosion, bent pins, or oil contamination. Using a digital multimeter, measure sensor resistance (typically 50-150 ohms at room temperature) and check harness continuity to the ECM (pins should show less than 5 ohms resistance).

Step 3: Pressure Verification Install a mechanical oil pressure gauge into the sensor port to verify actual pressure. Start the engine and compare mechanical gauge readings against ECM values. If mechanical pressure is adequate (300+ kPa at operating temperature) but the code persists, replace the sensor. If mechanical pressure is low, investigate the oil pump, bearings, or internal engine wear.

Step 4: Used Equipment Considerations For used excavators, thoroughly inspect the wiring harness routing from sensor to ECM, checking for rub-through points against frame members or heat shields. Clean all connector terminals with electrical contact cleaner and apply dielectric grease. Verify oil filter quality and consider oil analysis to detect internal wear.

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Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu service manual for your specific serial number and seek professional assistance from certified technicians for complex repairs or if safety concerns exist.