Komatsu PC70-8 Fault Code E-24: Complete Diagnostic Guide

What is Komatsu PC70-8 Fault Code E-24?

Fault Code E-24 on the Komatsu PC70-8 indicates a malfunction in the hydraulic oil temperature sensor circuit or an abnormal temperature reading exceeding safe operating parameters. This code is triggered when the Electronic Control Module (ECM) detects either an open circuit, short circuit, or temperature values outside the manufacturer's specified range (typically above 110°C/230°F).

The hydraulic oil temperature sensor is critical for the PC70-8's performance management system. When hydraulic fluid overheats, it loses viscosity and lubrication properties, potentially causing catastrophic damage to pumps, motors, and control valves. The ECM uses this sensor data to protect the machine by limiting performance or initiating shutdown protocols.

Common Symptoms

When Code E-24 is active, operators typically experience:

• Warning light illumination on the instrument panel, often accompanied by an audible alarm
• Reduced hydraulic performance or automatic derate mode, limiting boom, arm, and bucket speed
• Erratic hydraulic operation with inconsistent response times
• Machine shutdown in severe cases where temperature thresholds are critically exceeded
• Display showing abnormally high or low temperature readings (or dashes indicating sensor failure)

Potential Causes

The most common technical reasons for E-24 on used PC70-8 excavators include:

• Faulty hydraulic oil temperature sensor due to age-related degradation or contamination
• Damaged wiring harness at known rub points near the hydraulic tank or along the chassis frame
• Corroded or loose connector pins at the sensor or ECM connection points
• Actual hydraulic oil overheating caused by clogged coolers, low oil levels, or failing cooling fans
• ECM internal fault (less common) affecting the sensor input circuit
• Aftermarket sensor incompatibility if previous repairs used non-OEM parts

How to Troubleshoot and Fix Code E-24

Step 1: Visual Inspection Begin by inspecting the hydraulic oil temperature sensor located on the hydraulic tank. Check the wiring harness for visible damage, particularly where it routes near moving components or sharp edges common in used machines. Examine connector pins for corrosion, bent terminals, or oil contamination.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure resistance across its terminals. Compare readings against Komatsu specifications (typically 200-400 ohms at 20°C). Check for continuity in the harness from sensor to ECM. Measure supply voltage at the connector (should be approximately 5V reference voltage from the ECM).

Step 3: Physical System Check Verify actual hydraulic oil temperature using an infrared thermometer. Check hydraulic oil level, inspect the hydraulic cooler for blockages, and ensure the cooling fan operates correctly. On used excavators, accumulated debris in cooler fins is extremely common.

Step 4: Component Replacement If testing confirms sensor failure, replace with a genuine Komatsu sensor (part number specific to PC70-8). Clear codes using Komatsu diagnostic software (KOMTRAX or compatible scan tool) and monitor during operation.

Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu service manual and consider professional technician assistance for complex electrical diagnostics or if you're unfamiliar with high-voltage systems.