Komatsu PC450-8 Fault Code E-27: Complete Diagnostic Guide

What is Komatsu PC450-8 Fault Code E-27?

Fault Code E-27 on the Komatsu PC450-8 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 system.

The hydraulic oil temperature sensor is critical for the PC450-8's performance management system. It provides real-time data to the ECM, which uses this information to regulate engine output, prevent overheating, and protect hydraulic components from thermal damage. When this sensor circuit fails, the machine cannot accurately monitor hydraulic system health, potentially leading to reduced efficiency or component damage if operated under extreme conditions.

Common Symptoms

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

• Warning light illumination on the instrument panel, specifically the hydraulic system indicator
• Reduced hydraulic performance or slower cycle times as the ECM enters protective derate mode
• Inaccurate temperature gauge readings showing either maximum, minimum, or erratic values
• Intermittent alarm sounds when the machine is under load or during warm-up
• Engine power limitation in some cases, as the ECM restricts output to prevent potential hydraulic system damage

Potential Causes

The most common technical reasons for E-27 on used PC450-8 excavators include:

• Sensor failure due to age-related degradation or thermal cycling damage
• Wiring harness damage at known rub points near the hydraulic tank and along the main boom
• Corroded or loose connector pins at the sensor plug or ECM interface
• Short circuit to ground caused by damaged insulation from hydraulic fluid contamination
• Open circuit in the sensor wiring due to vibration-induced wire breakage
• ECM internal fault (less common) affecting the sensor input circuit

How to Troubleshoot and Fix Code E-27

Step 1: Visual Inspection Begin by locating the hydraulic oil temperature sensor on the hydraulic tank. Inspect the wiring harness from sensor to ECM for visible damage, chafing, or hydraulic fluid contamination. On used excavators, pay special attention to harness routing near moving components and check all connector pins for corrosion or bent terminals.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure its resistance at operating temperature (typically 200-400 ohms at 80°C, but verify with Komatsu specifications). Check for continuity in the wiring harness and measure voltage supply at the sensor connector (should be approximately 5V reference voltage from the ECM).

Step 3: Component Replacement If the sensor tests outside specifications, replace it with a genuine Komatsu part to ensure proper calibration. If wiring shows damage, repair or replace the affected harness section, ensuring proper heat-shrink sealing and secure routing away from friction points.

Step 4: Clear Code and Verify Use Komatsu diagnostic software (KOMTRAX) or a compatible scan tool to clear the fault code. Operate the machine through a complete warm-up cycle and monitor for code recurrence.

Disclaimer: This guide provides general diagnostic information. For complex electrical issues or if you're uncomfortable performing these tests, consult a certified Komatsu technician or authorized service center to prevent further damage to your equipment.