Kobelco SK135SR-2 Fault Code E013: Meaning and Fix

What is Kobelco SK135SR-2 Fault Code E013?

Fault Code E013 on the Kobelco SK135SR-2 excavator indicates a malfunction in the engine coolant temperature sensor circuit. This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) detects an abnormal voltage signal from the coolant temperature sensor, suggesting either an open circuit, short circuit, or sensor failure.

The coolant temperature sensor plays a critical role in engine management by monitoring operating temperatures and sending data to the ECM. This information controls fuel injection timing, throttle response, and prevents overheating conditions. On used SK135SR-2 machines, this code can significantly impact performance, causing poor fuel economy, rough idling, and potential engine protection mode activation that limits machine productivity.

Common Symptoms

When Code E013 is active on your Kobelco SK135SR-2, you may experience:

• Engine warning light illuminated on the instrument panel (check engine lamp)
• Hard starting conditions, especially when the engine is cold
• Rough idle or erratic engine RPM fluctuations during warm-up
• Engine derating or reduced power output as a protective measure
• Cooling fan running continuously at high speed regardless of actual engine temperature
• Inaccurate temperature gauge readings or gauge stuck in one position

Potential Causes

The most common technical causes for E013 on used Kobelco SK135SR-2 excavators include:

• Faulty coolant temperature sensor due to internal resistance drift or element failure (common after 5,000+ operating hours)
• Damaged wiring harness between the sensor and ECM, particularly at flex points near the engine block where vibration causes wire chafing
• Corroded or loose electrical connectors at the sensor terminal—extremely common on machines operated in humid or coastal environments
• Short to ground in the sensor signal wire caused by insulation breakdown
• Open circuit from broken wires inside the harness insulation (not visible externally)
• ECM internal fault (rare, but possible on high-hour used machines)

How to Troubleshoot and Fix Code E013

Step 1: Visual Inspection Begin by locating the coolant temperature sensor on the engine block (typically near the thermostat housing). Inspect the sensor connector for corrosion, moisture, bent pins, or physical damage. On used excavators, check the wiring harness routing for rub points against the engine or frame—this is a frequent failure point on the SK135SR-2 due to engine vibration.

Step 2: Electrical Testing Disconnect the sensor connector and use a digital multimeter to measure sensor resistance. With the engine cold, resistance should typically read between 2,000-3,000 ohms (consult Kobelco specifications for exact values). As the sensor warms, resistance should decrease smoothly. An infinite reading indicates an open sensor; zero ohms suggests an internal short.

Step 3: Circuit Verification With the sensor disconnected, check for voltage supply at the harness connector—you should see approximately 5 volts reference voltage from the ECM. Test the signal wire for continuity back to the ECM and check for shorts to ground using your multimeter's continuity function.

Step 4: Harness and Connector Service For used machines, clean all electrical connectors with contact cleaner and apply dielectric grease to prevent future corrosion. Repair any damaged wiring with proper heat-shrink solder connections—avoid quick-splice connectors that can fail under vibration.

Step 5: Component Replacement If testing confirms sensor failure, replace with a genuine Kobelco or OEM-equivalent sensor. After installation, clear the fault code using Kobelco diagnostic software or a compatible J1939 diagnostic tool, then verify the code doesn't return after a full heating cycle.

Professional Tip for Used Excavators: Before replacing the sensor, always verify the ECM ground connections are clean and tight, as poor grounding can mimic sensor failures on older machines.

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Disclaimer: This guide provides general troubleshooting information for Code E013. Diagnostic procedures may vary based on machine serial number and configuration. Always consult the official Kobelco service manual for your specific SK135SR-2 model, and consider professional diagnostic support for complex electrical issues or if you're unfamiliar with excavator electronic systems.