Komatsu PC200LC-7 Fault Code E-31: Technical Guide

What is Komatsu PC200LC-7 Fault Code E-31?

Fault Code E-31 on the Komatsu PC200LC-7 indicates a malfunction in the engine speed sensor circuit or an abnormal signal from the crankshaft position sensor. This code is triggered when the Engine Control Module (ECM) detects an irregular signal pattern, no signal, or voltage readings outside the manufacturer's specified parameters from the engine speed detection system.

The engine speed sensor is critical for proper fuel injection timing, governor control, and overall engine performance on the Komatsu SAA6D102E-2 engine. When this sensor circuit fails, the ECM cannot accurately monitor engine RPM, leading to operational issues and potential protective shutdowns. For used excavators, this code often stems from sensor degradation or wiring issues related to machine hours and environmental exposure.

Common Symptoms

When Code E-31 is active, operators typically experience:

• Engine fails to start or cranks but won't fire due to lack of speed signal confirmation
• Sudden engine stalling during operation, especially under load
• Erratic engine RPM behavior or inability to maintain consistent idle speed
• Warning light illumination on the instrument cluster with possible audible alarm
• Loss of power or engine entering a protective derate mode limiting performance

Potential Causes

The most common technical reasons for E-31 appearing on used PC200LC-7 excavators include:

• Failed crankshaft position sensor due to internal component deterioration (common after 8,000+ operating hours)
• Damaged sensor wiring harness from vibration, heat exposure, or physical rubbing against the engine block near the flywheel housing
• Corroded or loose electrical connectors at the sensor or ECM connection points
• Worn flywheel ring gear teeth causing inconsistent magnetic pickup signals
• ECM internal fault affecting the sensor circuit processing (less common but possible on older machines)
• Contamination or metal debris buildup on the magnetic sensor tip reducing signal strength

How to Troubleshoot and Fix Code E-31

Step 1: Visual Inspection Begin by locating the engine speed sensor on the flywheel housing (driver's side of the engine). Inspect the sensor mounting for looseness, physical damage, or excessive oil leakage. Check the wiring harness from sensor to ECM for visible abrasion, particularly where it passes near moving components or sharp edges—a known wear point on used machines.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor connector and measure resistance across the sensor terminals. The SAA6D102E-2 engine speed sensor should read approximately 185-275 ohms at room temperature. Check for continuity in the wiring harness from sensor connector to ECM pins. Inspect connector terminals for corrosion or bent pins that may cause intermittent connections.

Step 3: Signal Testing and Component Replacement Connect Komatsu diagnostic software (KOMTRAX or compatible scan tool) to monitor live sensor signal voltage while cranking. A healthy sensor produces an AC voltage signal of 0.5-3.0 volts depending on cranking speed. If readings are absent or erratic, remove the sensor and inspect the flywheel ring gear teeth for damage. Clean the sensor tip with electrical contact cleaner and check the air gap (0.5-1.5mm specification). Replace the sensor if resistance or signal tests fail, ensuring proper torque (25-30 Nm) during reinstallation.

For used excavators, always check connector seals and apply dielectric grease to prevent future corrosion. Clear the code and perform a test cycle under load to confirm the repair.

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Disclaimer: This guide provides general troubleshooting information. For complex electrical diagnostics or if you're unsure about any procedure, consult a certified Komatsu technician or authorized service center. Always follow proper lockout/tagout procedures and manufacturer safety guidelines when working on heavy equipment.