What is Komatsu PC220-10 Fault Code S-6?

Fault Code S-6 on the Komatsu PC220-10 excavator indicates a malfunction in the engine oil pressure sensor circuit or an actual low engine oil pressure condition. This code is generated when the Engine Control Module (ECM) detects that oil pressure has dropped below the manufacturer's specified threshold or when the oil pressure sensor circuit shows an abnormal voltage reading outside the normal operating range of 0.5-4.5 volts.

This fault is critical for the PC220-10's SAA6D107E-1 engine because proper oil pressure ensures adequate lubrication of engine bearings, turbocharger components, and hydraulic system components. The ECM continuously monitors oil pressure through a dedicated sensor mounted on the engine block. When pressure falls below approximately 50 kPa (7.3 psi) at idle or 200 kPa (29 psi) at rated speed, the system triggers this code to prevent catastrophic engine damage.

Common Symptoms

When Code S-6 is active on your Komatsu PC220-10, operators typically experience:

• Engine warning light illuminated on the monitor panel, often accompanied by an audible alarm
• Engine derate mode activated, limiting RPM to protect internal components from damage
• Noticeable reduction in hydraulic response and digging force due to decreased engine output
• Low oil pressure warning message displayed on the multi-function monitor screen
• In severe cases, automatic engine shutdown to prevent seized bearings or crankshaft damage

Potential Causes

The most common technical reasons for Code S-6 appearing on used PC220-10 excavators include:

• Faulty oil pressure sensor – The sensor's internal diaphragm deteriorates over time, especially on machines with 5,000+ operating hours
• Low engine oil level – Oil consumption through worn piston rings or external leaks (common at valve cover gaskets and front crankshaft seal on used machines)
• Wiring harness damage – The sensor harness near the starter motor is prone to abrasion from vibration, creating intermittent open circuits
• Clogged oil filter – Restricted oil flow from contaminated or overdue filters increases pressure drop across the system
• Worn oil pump – Internal wear on pump gears reduces flow capacity, particularly in excavators exceeding 8,000 hours
• ECM connector corrosion – Moisture infiltration at the engine harness connector (often due to damaged wire boots) causes voltage irregularities

How to Troubleshoot and Fix Code S-6

Step 1: Initial System Checks Start by verifying actual engine oil level with the machine on level ground and engine off for 10 minutes. Check oil quality – metallic particles or milky appearance indicate internal engine damage. Using Komatsu KOMTRAX or an aftermarket diagnostic scanner, check if the code is active or stored (historical).

Step 2: Sensor Circuit Testing Locate the oil pressure sensor on the left side of the engine block, below the fuel filter assembly. Disconnect the three-pin connector and use a digital multimeter to measure resistance. The sensor should read 100-300 ohms at room temperature. Check harness continuity from the sensor connector to ECM pin E2-23 – resistance should be less than 5 ohms, with no continuity to ground (infinite resistance).

Step 3: Voltage and Signal Verification With ignition on (engine off), measure voltage at the sensor connector. You should see approximately 5 volts on the signal wire (red wire) and proper ground (less than 0.1 volts) on the black wire. If voltage is incorrect, inspect the engine harness for damage, particularly where it passes near the starter motor mounting bracket – this is a known rub point on used PC220-10s.

Step 4: Pressure Testing and Component Inspection If electrical checks pass, install a mechanical oil pressure gauge in the sensor port. Start the engine and verify actual pressure: minimum 100 kPa (14.5 psi) at idle warm, 400-500 kPa (58-73 psi) at high idle. Low readings indicate mechanical issues requiring oil pump inspection, bearing clearance checks, or filter replacement. On used excavators, always inspect connector terminals for corrosion and apply dielectric grease before reassembly.

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Disclaimer: This guide provides general troubleshooting information. Always consult the official Komatsu service manual for your specific machine serial number and seek professional assistance from certified technicians for complex engine repairs. Improper diagnostics may lead to equipment damage or safety hazards.