Komatsu PC60-7 Fault Code S-2: Complete Diagnostic Guide

What is Komatsu PC60-7 Fault Code S-2?

Fault Code S-2 on the Komatsu PC60-7 indicates a malfunction in the engine revolution sensor circuit. This code specifically signals that the ECM (Engine Control Module) is not receiving proper signals from the crankshaft position sensor or related wiring, preventing accurate monitoring of engine speed and timing.

This sensor is critical for the PC60-7's diesel engine performance because it provides real-time data about crankshaft rotation to the ECM. Without accurate readings, the control module cannot properly manage fuel injection timing, engine speed control, or emission systems. In used excavators, this fault commonly stems from sensor deterioration, corroded connections, or damaged wiring harnesses—issues that accumulate over years of operation in harsh construction environments.

Common Symptoms

When fault code S-2 is active on your Komatsu PC60-7, you may experience:

• Engine cranks but fails to start or experiences extended cranking before starting
• Intermittent stalling during operation, especially at idle or low RPM
• Erratic engine RPM with noticeable fluctuations under load
• Warning lamp illuminated on the instrument panel
• Loss of power or inability to reach maximum engine speed

Potential Causes

The most common technical causes for S-2 on used PC60-7 excavators include:

• Failed crankshaft position sensor due to age, heat exposure, or internal component breakdown
• Damaged wiring harness with broken wires or shorts, particularly at flex points near the engine mounting
• Corroded or loose connectors at the sensor or ECM interface—extremely common in machines operating in wet or marine environments
• Air gap issues between the sensor and flywheel ring gear due to mounting bracket wear or sensor misalignment
• ECM power supply problems affecting sensor voltage reference signals
• Contaminated sensor face from metal debris or oil accumulation on older machines

How to Troubleshoot and Fix Code S-2

Step 1: Visual Inspection Begin by locating the crankshaft position sensor on the engine block near the flywheel housing. Inspect the wiring harness for obvious damage, chafing, or connector corrosion. On used excavators, pay special attention to harness routing where vibration causes wire friction against metal surfaces.

Step 2: Connector and Voltage Testing Disconnect the sensor connector and inspect pins for corrosion or damage. Using a digital multimeter, check for proper reference voltage (typically 5V or 12V depending on sensor type) at the harness connector with ignition on. Verify ground continuity between the sensor ground pin and chassis ground (should read less than 1 ohm).

Step 3: Sensor Resistance Check Test the sensor resistance by measuring across sensor terminals (typically 150-300 ohms for inductive sensors, though consult service manual for exact specifications). Replace the sensor if readings are out of specification or infinite.

Step 4: Air Gap Verification Check the air gap between the sensor tip and flywheel teeth using a feeler gauge (typical specification: 0.5-1.5mm). Adjust mounting if necessary, as bracket wear in older machines often causes excessive gap.

Step 5: Advanced Diagnostics If basic tests pass, use Komatsu diagnostic software to monitor live sensor data during cranking. This identifies intermittent signal dropouts that point to internal sensor failure or ECM input circuit problems.

Disclaimer: This guide provides general troubleshooting procedures. Always consult the official Komatsu service manual for your specific serial number. If you're unsure about electrical diagnostics, consult a certified heavy equipment technician to prevent further damage to electrical systems.