What is Kobelco SK130-8 Fault Code 6574?

Fault Code 6574 on the Kobelco SK130-8 excavator indicates a malfunction in the engine coolant temperature sensor circuit, specifically a voltage signal that is out of the normal operating range or an intermittent connection. This diagnostic trouble code (DTC) is logged by the Engine Control Module (ECM) when it detects an abnormal reading from the coolant temperature sensor, which monitors the operating temperature of the Isuzu engine used in this model.

This code is critical because the ECM relies on accurate coolant temperature data to optimize fuel injection timing, regulate engine speed, and prevent overheating. When Code 6574 is active, the engine may operate in a failsafe or derate mode, reducing performance and potentially causing costly downtime on job sites. For used excavators like the SK130-8, sensor degradation and wiring harness issues are common triggers.

Common Symptoms

When Fault Code 6574 is active on your Kobelco SK130-8, you may experience:

• Check engine light or warning indicator illuminated on the instrument panel
• Engine running in derate mode with reduced power output and slower hydraulic response
• Difficulty starting the engine, especially in cold weather conditions
• Engine cooling fan running continuously at high speed regardless of actual temperature
• Inaccurate temperature gauge readings or erratic fluctuations on the display

Potential Causes

Several mechanical and electrical issues can trigger Code 6574 on used SK130-8 excavators:

• Failed coolant temperature sensor due to internal element degradation or physical damage
• Corroded or loose electrical connector at the sensor or ECM harness junction
• Damaged sensor wiring harness caused by rubbing against the engine block or frame (common wear point near the thermostat housing)
• ECM internal fault affecting the temperature sensor circuit processing
• Incorrect coolant level or air pockets in the cooling system creating false readings
• Previous aftermarket repairs using non-OEM sensors with incorrect resistance specifications

How to Troubleshoot and Fix Code 6574

Step 1: Visual Inspection Begin by locating the coolant temperature sensor on the engine block near the thermostat housing. Inspect the sensor body for physical damage, coolant leaks, or corrosion. Check the wiring harness from the sensor to the ECM for chafing, breaks, or exposure to heat damage—particularly where the harness passes near exhaust components or moving parts.

Step 2: Electrical Testing Disconnect the sensor connector and use a digital multimeter to measure resistance across the sensor terminals. At room temperature (68°F/20°C), resistance should typically read between 2,000-3,000 ohms (consult your service manual for exact specifications). Test the harness side for continuity to the ECM and check for short circuits to ground. Voltage supply from the ECM should read approximately 5 volts with the key on, engine off.

Step 3: Component Replacement and Verification If resistance values are outside specifications or the sensor shows physical deterioration, replace with a genuine Kobelco or OEM-equivalent sensor. For used excavators, always apply dielectric grease to connector pins to prevent future corrosion. After replacement, clear the fault code using diagnostic software (such as Kobelco's service tool or compatible scanner) and perform a test run, monitoring live coolant temperature data to ensure the ECM receives proper signals.

Disclaimer: This guide provides general troubleshooting information. Always consult the Kobelco SK130-8 service manual and consider professional diagnosis for complex electrical issues or if you lack proper diagnostic equipment.