What is Komatsu PC210LC-10 Fault Code S-8?

Fault Code S-8 on the Komatsu PC210LC-10 indicates a malfunction in the fuel injection system, specifically related to the fuel injection quantity control or fuel rail pressure sensor circuit. This code is triggered when the Engine Control Module (ECM) detects abnormal signals from the fuel pressure monitoring system or when actual fuel delivery deviates from commanded parameters.

The PC210LC-10 uses a common rail fuel injection system with precise electronic control to optimize combustion efficiency and meet emissions standards. When the ECM cannot maintain proper fuel rail pressure or receives inconsistent sensor data, it logs S-8 to protect the engine from potential damage due to improper fuel delivery. This fault directly impacts engine performance, fuel economy, and can lead to costly engine damage if ignored in used machinery where wear patterns may already exist.

Common Symptoms

• Engine power loss or derate mode – The excavator may run with significantly reduced horsepower to prevent engine damage
• Hard starting or extended cranking time – Especially noticeable during cold starts when fuel pressure is critical
• Rough idle or engine misfiring – Inconsistent fuel delivery causes uneven combustion
• Black or white exhaust smoke – Indicates improper fuel atomization or overfueling conditions
• Warning lamp illumination on the instrument cluster with possible audible alarm

Potential Causes

• Fuel rail pressure sensor failure – Common in used excavators with 5,000+ hours due to heat cycling and vibration
• Damaged or corroded wiring harness at connector points near the engine block where harness routing causes friction wear
• Fuel injection pump wear – Internal components lose tolerance in high-hour machines, affecting pressure regulation
• Clogged fuel filters restricting flow and preventing proper rail pressure buildup
• ECM calibration issues or software corruption – particularly in machines with prior electrical system problems
• Faulty pressure relief valve in the common rail assembly sticking open or closed

How to Troubleshoot and Fix Code S-8

Step 1: Connect Diagnostic Software Use Komatsu KOMTRAX or compatible diagnostic software to read live fuel rail pressure data. Compare actual pressure readings (typically 1,200-1,800 bar at rated load) against commanded values. Document any deviation greater than 10%.

Step 2: Inspect Fuel Pressure Sensor and Wiring Locate the fuel rail pressure sensor on the common rail assembly. Disconnect the connector and inspect for corrosion, moisture, or damaged pins – extremely common in used excavators. Using a digital multimeter, check sensor resistance (typically 200-300 ohms at 20°C). Inspect the entire harness routing from sensor to ECM, paying special attention to areas where the harness contacts the engine block or frame rails.

Step 3: Test Fuel System Mechanical Components Check fuel filter condition and replace if service hours exceed recommendations. Perform a fuel return flow test to verify injection pump output. On used machines, inspect all fuel line connections for weeping or air infiltration. Check the pressure relief valve operation by monitoring pressure during loaded conditions.

Step 4: Verify ECM Functionality If sensors and mechanical components test within specifications, the ECM may require reprogramming or replacement. Check for ECM software updates from Komatsu that address fuel system control issues specific to the PC210LC-10.

Disclaimer: This guide provides general troubleshooting information. Always consult the official Komatsu service manual and consider professional diagnostic services for complex fuel system repairs. Improper repairs can cause catastrophic engine failure.