What is Komatsu PC210-10 Fault Code S-15?

Fault Code S-15 on the Komatsu PC210-10 excavator indicates a malfunction in the swing motor secondary pressure sensor circuit. This code triggers when the Engine Control Module (ECM) detects an abnormal voltage signal from the sensor that monitors hydraulic pressure in the swing motor's secondary circuit.

The swing motor secondary pressure sensor plays a critical role in the PC210-10's advanced hydraulic system by providing real-time pressure data to the controller. This information allows the ECM to optimize swing performance, prevent system overloads, and ensure smooth deceleration during slewing operations. When this sensor circuit malfunctions, the machine may enter a protective derate mode to prevent potential damage to the hydraulic swing motor assembly, which is especially important in used excavators where component wear accumulates over time.

Common Symptoms

When fault code S-15 is active on your Komatsu PC210-10, operators typically experience:

• Swing function limitations or complete loss of swing capability in one or both directions
• Illuminated warning lamp on the monitor panel with specific S-15 code display
• Erratic swing motor performance, including jerky or inconsistent rotation speeds
• Automatic engine derate or power reduction to protect hydraulic components
• Audible alarm accompanying the visual warning on the operator display

Potential Causes

The most common technical reasons for S-15 fault code activation include:

• Damaged or corroded wiring harness connections at the swing motor pressure sensor (common wear point on used machines due to constant rotational movement)
• Failed swing motor secondary pressure sensor due to internal component degradation or contamination
• Broken or frayed wires in the sensor harness where it passes through the center joint area
• Poor ground connections causing voltage reference issues
• ECM internal fault or corrupted calibration data (less common)
• Hydraulic contamination causing sensor membrane damage in older excavators

How to Troubleshoot and Fix Code S-15

Step 1: Visual Inspection Begin by accessing the swing motor assembly and thoroughly inspect the secondary pressure sensor and its wiring harness. On used PC210-10 excavators, pay special attention to the center joint area where harnesses are subjected to repeated flexing. Look for abraded insulation, corroded connectors, or physical damage to the sensor body.

Step 2: Electrical Testing Using a quality digital multimeter, check the sensor's output voltage with the ignition on (engine off). The sensor should typically read between 0.5-4.5 volts depending on system pressure. Verify harness continuity between the sensor connector and the ECM pins according to Komatsu's wiring diagram. Check resistance values against factory specifications (typically 100-500 ohms for the sensor circuit).

Step 3: Connector and Ground Verification Disconnect the sensor connector and inspect for corrosion, bent pins, or moisture intrusion—common issues in aging equipment. Clean connections with electrical contact cleaner and apply dielectric grease. Verify ground circuit integrity, as poor grounds frequently cause erratic sensor readings in excavators with high operating hours.

Step 4: Component Replacement If electrical tests confirm sensor failure, replace the swing motor secondary pressure sensor with a genuine Komatsu part. For used excavators, simultaneously replace the connector pigtail if any corrosion is present to prevent repeat failures.

Step 5: System Verification After repairs, clear fault codes using Komatsu diagnostic software (KOMTRAX or dealer-level tools). Perform a complete swing function test under load and monitor live sensor data to confirm proper pressure readings throughout the operating range.

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Disclaimer: This guide provides general troubleshooting information for experienced technicians. Always consult the official Komatsu PC210-10 service manual and consider professional diagnostic assistance for complex hydraulic-electrical issues, especially when working with high-pressure systems.