What is Komatsu PC210LC-10 Fault Code E-27?

Fault Code E-27 on the Komatsu PC210LC-10 indicates a malfunction in the hydraulic oil temperature sensor circuit. This code triggers when the Engine Control Module (ECM) detects an abnormal voltage signal from the temperature sensor monitoring the hydraulic oil, typically indicating an open circuit, short circuit, or sensor failure.

The hydraulic oil temperature sensor plays a critical role in protecting the PC210LC-10's hydraulic system by monitoring operating temperatures and preventing overheating damage. When this sensor fails or sends erratic signals, the ECM cannot accurately assess hydraulic system health, potentially leading to inadequate cooling, component wear, or catastrophic hydraulic failure. For used excavators, this code often appears due to sensor degradation, corroded connectors, or damaged wiring harnesses from years of vibration and environmental exposure.

Common Symptoms

When Code E-27 is active, operators typically experience:

• Warning light illumination on the instrument cluster, often accompanied by an audible alarm
• Inaccurate hydraulic temperature readings on the monitor display, showing extremely high, low, or fluctuating values
• Potential derate mode activation where hydraulic function speed may be reduced as a protective measure
• Intermittent code activation during machine operation, especially during temperature changes or when operating on uneven terrain
• ECM logging multiple instances of the fault, visible through Komatsu diagnostic software (KOMTRAX or PC-based diagnostics)

Potential Causes

The most common technical causes for E-27 on used PC210LC-10 excavators include:

• Failed hydraulic oil temperature sensor due to internal component degradation or contamination from extended service life
• Corroded or loose electrical connectors at the sensor harness connection point, particularly common in machines exposed to moisture or extreme environments
• Damaged wiring harness from abrasion against the hydraulic tank or frame, especially at known rub points near the tank mounting area
• Faulty ECM connections or internal ECM issues affecting the sensor circuit input
• Contaminated hydraulic oil causing sensor element coating or failure
• Poor ground connections in the sensor circuit creating voltage irregularities

How to Troubleshoot and Fix Code E-27

Step 1: Visual Inspection Begin by locating the hydraulic oil temperature sensor, typically mounted on the hydraulic oil tank. Inspect the sensor body for physical damage, oil leaks, or corrosion. Examine the wiring harness from the sensor to the ECM, checking for abraded insulation, pinched wires, or damage at known rub points along the tank and frame. On used excavators, pay special attention to connector pins for corrosion or bent terminals.

Step 2: Electrical Testing Disconnect the sensor connector and use a digital multimeter to measure sensor resistance. Consult the Komatsu service manual for specifications (typically 200-400 ohms at 20°C, varying with temperature). Test the harness continuity from the sensor connector to the ECM using a wiring diagram. Check for shorts to ground by measuring resistance between each wire and machine ground (should read infinite resistance).

Step 3: Voltage and Signal Testing With the key on and engine off, check reference voltage at the sensor connector (should be approximately 5 volts from the ECM). If voltage is absent or incorrect, trace back to the ECM for harness issues or ECM problems. Use Komatsu diagnostic software to monitor live sensor data and compare actual hydraulic temperature with sensor readings.

Step 4: Component Replacement If testing confirms sensor failure, replace with a genuine Komatsu sensor or high-quality OEM equivalent. Apply dielectric grease to connector pins to prevent future corrosion. After replacement, clear codes using diagnostic software and operate the machine through a complete heat cycle to verify proper sensor function and code resolution.

Disclaimer: This guide provides general troubleshooting information. Always consult the official Komatsu service manual for your specific machine serial number. Complex electrical diagnostics or ECM replacement should be performed by qualified Komatsu technicians with proper diagnostic equipment.