Komatsu PC220-10 Fault Code E-37: Complete Diagnostic Guide

What is Komatsu PC220-10 Fault Code E-37?

Fault Code E-37 on the Komatsu PC220-10 indicates a hydraulic oil temperature sensor circuit malfunction or abnormal temperature reading in the hydraulic system. This code triggers when the Engine Control Module (ECM) detects either an open circuit, short circuit, or implausible voltage signal from the hydraulic oil temperature sensor located in the main hydraulic tank.

This diagnostic trouble code is critical for the PC220-10's performance because the hydraulic oil temperature directly affects system efficiency, component longevity, and operational safety. When the ECM cannot accurately monitor hydraulic temperatures, the machine may enter derate mode to prevent potential damage to pumps, motors, and cylinder seals that can occur from overheated hydraulic fluid.

Common Symptoms

When Code E-37 is active on your Komatsu PC220-10, operators typically experience:

• Warning lamp illumination on the monitor panel with fault code display
• Reduced hydraulic performance or slower cycle times as the machine enters protective mode
• Erratic temperature gauge readings or temperature display showing implausible values (extremely high or low)
• Intermittent power loss during operation, especially under heavy load conditions
• Audible warning alarms accompanying the visual fault indication

Potential Causes

The most common technical reasons for E-37 appearing on used PC220-10 excavators include:

• Damaged or corroded sensor connector at the hydraulic tank (prone to moisture intrusion on machines with high hours)
• Failed hydraulic oil temperature sensor due to internal component degradation or physical damage
• Wiring harness chafing at known rub points near the hydraulic tank mounting area or along the main chassis harness
• Broken or frayed wiring between the sensor and ECM connection points
• ECM connector corrosion affecting signal reception (common in machines operating in wet or coastal environments)
• Contaminated hydraulic oil causing actual overheating that triggers protective fault logging

How to Troubleshoot and Fix Code E-37

Step 1: Visual Inspection Begin with a thorough inspection of the hydraulic oil temperature sensor located on the hydraulic tank. Check the connector pins for corrosion, bent terminals, or moisture accumulation. On used excavators, pay special attention to connector seal integrity as deteriorated O-rings allow contaminants to enter. Inspect the wiring harness from the sensor to the ECM for visible damage, especially where it routes near moving components or sharp edges.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure resistance across the sensor terminals. The PC220-10 hydraulic temperature sensor should typically read 2,000-3,000 ohms at 77°F (25°C) (consult your service manual for exact specifications). Test for continuity along the wiring harness and check for short circuits to ground. Measure the reference voltage at the ECM connector (usually 5 volts) to confirm proper signal supply.

Step 3: Sensor and Harness Replacement If electrical values fall outside specifications, replace the faulty component. For used machinery, consider replacing both the sensor and connector together, as aged connectors often fail shortly after sensor replacement. Use dielectric grease on all electrical connections to prevent future corrosion. Clear the fault code using Komatsu diagnostic software (KOMTRAX or PC service software) and perform a complete operational test under load.

Step 4: Verify Hydraulic System Health Before concluding repairs, check actual hydraulic oil temperature and condition. Contaminated or degraded oil can cause genuine overheating that repeatedly triggers E-37. Inspect hydraulic cooler function and verify proper oil levels.

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Disclaimer: This guide provides general diagnostic information for Komatsu PC220-10 excavators. Always consult the official Komatsu service manual for your specific machine serial number and consider professional diagnosis for complex electrical issues. Improper repairs may void warranties or cause additional damage.