What is Komatsu PC200-10 Fault Code E-31?

Fault Code E-31 on the Komatsu PC200-10 excavator indicates a malfunction in the throttle position sensor (TPS) circuit or an abnormal signal being received by the engine control module (ECM). This code specifically points to either an out-of-range voltage signal, a sensor calibration issue, or a communication fault between the throttle position sensor and the ECM.

The throttle position sensor is critical for the PC200-10's performance because it directly informs the ECM about the operator's power demand. The ECM uses this data to regulate fuel injection timing, engine RPM, and hydraulic pump flow. When E-31 is active, the machine's ability to respond properly to throttle inputs becomes compromised, potentially causing inefficient fuel consumption, reduced power output, or erratic engine behavior. For used excavators, this code often emerges due to sensor wear or harness degradation from prolonged vibration and environmental exposure.

Common Symptoms

When fault code E-31 is active on a Komatsu PC200-10, operators typically experience:

• Engine hesitation or erratic RPM when moving the throttle dial or under load conditions
• Illuminated warning lights on the instrument cluster, often the engine malfunction indicator
• Reduced engine power or derated performance, with the ECM limiting power to prevent damage
• Intermittent loss of throttle response, especially during startup or after the machine has been sitting
• Unusual fluctuations in hydraulic system performance due to inconsistent engine speed regulation

Potential Causes

Several technical issues can trigger E-31 on used PC200-10 excavators:

• Throttle position sensor failure due to internal component wear, carbon buildup, or calibration drift
• Damaged or corroded wiring harness between the TPS and ECM, particularly at connector pins exposed to moisture
• Loose or oxidized electrical connectors at the sensor mounting point or ECM interface
• ECM software issues or corrupted calibration data (less common but possible in older machines)
• Voltage supply problems from the machine's electrical system, including poor grounding points
• Physical damage to the TPS mounting bracket causing misalignment or excessive sensor movement during operation

How to Troubleshoot and Fix Code E-31

Step 1: Visual Inspection and Connector Check Begin by inspecting the throttle position sensor located on the fuel injection pump or governor assembly. Check all electrical connectors for corrosion, bent pins, or moisture intrusion. On used excavators, pay special attention to harness routing where cables may rub against the engine block or frame—a common wear point on the PC200-10. Clean all connections with electrical contact cleaner and ensure secure seating.

Step 2: Electrical Testing with Diagnostic Tools Using a digital multimeter, measure the voltage output from the TPS while slowly moving the throttle from idle to full position. The voltage should sweep smoothly (typically 0.5V to 4.5V range, consult Komatsu service manual for exact specifications). Check for resistance values between sensor terminals—erratic readings or open circuits indicate sensor failure. Also verify the 5-volt reference supply from the ECM to the sensor and ensure proper ground continuity (less than 1 ohm resistance).

Step 3: Advanced Diagnostics and Component Replacement Connect Komatsu diagnostic software (KOMTRAX Plus or equivalent) to monitor real-time sensor data and compare against factory parameters. If voltage signals are irregular or stuck, replace the throttle position sensor with a genuine Komatsu part. Before installation, inspect the sensor mounting surface for damage and apply dielectric grease to connectors. After replacement, perform an ECM relearn procedure using diagnostic software to calibrate the new sensor. Clear the fault code and conduct a full operational test under load.

For used excavators, always verify harness integrity along the entire run from sensor to ECM, as vibration-induced wire fatigue is a frequent culprit that can cause codes to return even after sensor replacement.

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Disclaimer: This guide provides general troubleshooting information for educational purposes. Always consult the official Komatsu PC200-10 service manual and consider professional diagnostic assistance for complex electrical issues. Improper repairs may lead to further machine damage or safety hazards.