Komatsu PC210-10 Fault Code E-27: Complete Diagnostic Guide

What is Komatsu PC210-10 Fault Code E-27?

Fault Code E-27 on the Komatsu PC210-10 indicates a malfunction in the hydraulic oil temperature sensor circuit. This code is triggered when the Engine Control Module (ECM) detects an abnormal voltage reading from the temperature sensor monitoring the hydraulic oil in the main system.

The hydraulic oil temperature sensor plays a critical role in protecting the PC210-10's hydraulic system. It monitors oil temperature to prevent overheating damage to pumps, motors, and seals. When this sensor fails or sends incorrect signals, the ECM cannot accurately regulate system performance, potentially leading to reduced efficiency or component damage. For used excavators, this code frequently appears due to sensor degradation or wiring issues common in machines with high operating hours.

Common Symptoms

When Code E-27 is active on your Komatsu PC210-10, you may experience:

• Hydraulic temperature warning light illuminated on the monitor panel
• Reduced hydraulic performance or slower cycle times as the system enters protective derate mode
• Inaccurate temperature readings displayed on the monitoring system (showing extremely high or low values)
• Intermittent code activation that clears and returns, especially during temperature fluctuations
• Possible activation of backup cooling fans even when hydraulic oil temperature is normal

Potential Causes

The most common technical causes for E-27 on used PC210-10 excavators include:

• Failed hydraulic oil temperature sensor due to internal element deterioration (common after 6,000+ operating hours)
• Corroded or loose connector pins at the sensor or ECM harness connection points
• Damaged wiring harness from rubbing against the hydraulic tank or frame components
• Short circuit to ground or power in the sensor signal wire
• Contaminated hydraulic oil causing sensor element coating and false readings
• ECM internal fault (rare, but possible in high-hour machines)

How to Troubleshoot and Fix Code E-27

Step 1: Visual Inspection Begin by locating the hydraulic oil temperature sensor on the main hydraulic tank. Inspect the wiring harness from the sensor to the ECM for visible damage, wear points, or oil contamination. On used excavators, check where the harness routes near the swing motor and tank mounting brackets—common rub-through points on the PC210-10.

Step 2: Connector and Resistance Testing Disconnect the sensor connector and inspect for corrosion, bent pins, or oil intrusion. Using a digital multimeter, measure the sensor's resistance. At room temperature (20°C/68°F), resistance should typically read between 2,000-3,000 ohms. Compare readings against Komatsu's specification chart for temperature-to-resistance values. A reading of infinite resistance or near-zero indicates sensor failure.

Step 3: Circuit Voltage Check With the sensor disconnected and ignition on, measure voltage at the harness-side connector. You should see approximately 5 volts on the signal wire (reference your PC210-10 wiring diagram for pin identification). No voltage indicates a wiring issue or ECM problem. If voltage is present but the sensor tests faulty, replace the temperature sensor.

Step 4: Harness Continuity Test If the sensor tests good, check harness continuity from the sensor connector to the ECM pins using the multimeter's continuity function. Wiggle the harness while testing to identify intermittent breaks common in used machines.

Step 5: Clear Code and Monitor After repairs, use Komatsu diagnostic software (KOMTRAX or equivalent diagnostic tool) to clear the fault code. Operate the machine through a full heating cycle and monitor for code recurrence.

Disclaimer: This guide provides general diagnostic information for the Komatsu PC210-10. Always consult the official Komatsu service manual for your specific machine's serial number range. If you're uncomfortable performing electrical diagnostics, consult a certified Komatsu technician to avoid damaging the ECM or hydraulic system components.