Komatsu PC160LC-7 Fault Code E-31: Complete Diagnostic Guide

What is Komatsu PC160LC-7 Fault Code E-31?

Fault Code E-31 on the Komatsu PC160LC-7 indicates a malfunction in the hydraulic pump delivery pressure sensor circuit. This code specifically signals that the Engine Control Module (ECM) has detected abnormal voltage readings from the pump pressure sensor, which monitors the main hydraulic pump's output pressure.

This sensor plays a critical role in the PC160LC-7's performance management system. The ECM uses pressure data to optimize engine output, prevent overload conditions, and protect the hydraulic system from damage. When E-31 triggers, the machine's control system cannot accurately monitor hydraulic system pressure, potentially leading to reduced performance or protective derate modes that limit the excavator's operational capabilities.

Common Symptoms

When Code E-31 is active on your PC160LC-7, operators typically experience:

• Warning light illumination on the monitor panel, often accompanied by an audible alarm
• Reduced hydraulic power or sluggish operation of boom, arm, and bucket functions
• Engine derate mode engagement, limiting maximum RPM to protect the system
• Erratic hydraulic response during simultaneous multi-function operations
• Intermittent loss of power especially under heavy load conditions or when the machine reaches operating temperature

Potential Causes

The most common technical reasons for E-31 in used PC160LC-7 excavators include:

• Faulty hydraulic pump pressure sensor due to internal component degradation or contamination
• Damaged wiring harness between the sensor and ECM, particularly at known rub points near the pump mounting area
• Corroded or loose electrical connectors at the sensor or ECM junction points (common in machines with high operating hours)
• Contaminated hydraulic oil causing sensor membrane damage or reading inconsistencies
• ECM internal fault preventing proper signal interpretation (less common but possible in older units)
• Voltage supply issues from the main power harness affecting sensor excitation voltage

How to Troubleshoot and Fix Code E-31

Step 1: Initial Visual Inspection Begin by inspecting the hydraulic pump pressure sensor located on the main pump assembly. Check for physical damage, oil leaks around the sensor body, or loose mounting. Examine the wiring harness from the sensor to the ECM for signs of abrasion, cuts, or wear at flex points—particularly where the harness passes near the pump or along the frame rail.

Step 2: Electrical Testing Using a digital multimeter, check the sensor's power supply voltage (should be approximately 5V DC). Disconnect the sensor connector and measure resistance across the sensor terminals; typical values range from 200-500 ohms (consult your service manual for exact specifications). Test harness continuity from sensor to ECM and check for short circuits to ground.

Step 3: Advanced Diagnostics Connect Komatsu diagnostic software (KOMTRAX or PC-based diagnostic tool) to monitor live sensor data. Compare actual pressure readings with expected values during idle and loaded conditions. For used excavators, pay special attention to connector corrosion—clean all pins with electrical contact cleaner and apply dielectric grease before reconnection.

Step 4: Component Replacement If testing confirms sensor failure, replace with a genuine Komatsu pressure sensor (part number specific to PC160LC-7). Before installation, verify hydraulic oil condition and change if contaminated. Clear codes using diagnostic software and perform a complete operational test under load.

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Disclaimer: This guide provides general troubleshooting information for experienced technicians. Always consult the official Komatsu service manual for your specific machine serial number. If unfamiliar with hydraulic systems or electrical diagnostics, contact a certified Komatsu dealer or qualified heavy equipment technician to prevent injury or further damage.