What is Kobelco SK350LC-8 Fault Code D013?

Kobelco SK350LC-8 Fault Code D013 indicates a malfunction in the engine coolant temperature sensor circuit, specifically detecting an abnormal voltage signal or out-of-range reading from the coolant temperature sensor to the Engine Control Module (ECM). This sensor plays a critical role in monitoring engine operating temperature and directly influences fuel injection timing, idle speed control, and fan operation on this Isuzu-powered excavator model.

The coolant temperature sensor is a thermistor-type component that changes electrical resistance based on engine temperature. When this circuit fails, the ECM cannot accurately regulate engine performance parameters, potentially leading to increased fuel consumption, rough operation, or inadequate engine protection during thermal stress situations. For the SK350LC-8's Isuzu 6HK1X engine, maintaining proper temperature monitoring is essential for preventing costly overheating damage and ensuring optimal hydraulic system performance.

Common Symptoms

When Code D013 is active on your Kobelco SK350LC-8, operators typically experience:

• Check engine warning light illuminated on the instrument panel, sometimes accompanied by audible alarm
• Engine fan running continuously at high speed, regardless of actual coolant temperature
• Rough or erratic idle speed, particularly during cold starts or warm-up periods
• Reduced hydraulic response or power, as the ECM may enter a derated protection mode
• Black smoke from exhaust due to incorrect fuel mapping when temperature data is unavailable

Potential Causes

The most common technical reasons for D013 appearing on used SK350LC-8 excavators include:

• Coolant temperature sensor failure due to age-related internal resistance drift or contamination from coolant additives
• Wiring harness damage at known rub points near the thermostat housing or along the right-side engine harness routing
• Corroded or loose connector pins at the sensor plug, especially common in machines exposed to humid or marine environments
• ECM internal circuit degradation affecting the 5-volt reference supply to the sensor
• Damaged sensor mounting threads causing poor thermal contact with coolant passages, resulting in inaccurate readings

How to Troubleshoot and Fix Code D013

Step 1: Visual Inspection Begin by locating the coolant temperature sensor on the left side of the cylinder head near the thermostat housing. Disconnect the 2-pin connector and carefully inspect for corrosion, bent pins, or moisture intrusion. On used excavators, this connector frequently shows green corrosion buildup—clean with electrical contact cleaner and verify pin tension.

Step 2: Sensor Resistance Testing Using a digital multimeter, measure resistance across the sensor terminals. At room temperature (68°F/20°C), expect approximately 2,500-3,000 ohms. Compare against Kobelco specifications at various temperatures. If readings are infinite (open circuit) or near zero (short circuit), replace the sensor with a genuine Kobelco or OEM-equivalent part.

Step 3: Circuit Voltage Check With the sensor disconnected and ignition ON (engine OFF), measure voltage at the harness connector. You should find approximately 5 volts on the signal wire and solid ground (0.05V or less) on the ground wire. If voltage is absent, trace the wiring harness back to the ECM connector C-136, checking for breaks or harness chafing at bulkhead pass-throughs.

Step 4: Advanced Diagnostics Connect Kobelco MAPS diagnostic software or compatible Isuzu diagnostic tool to verify real-time temperature readings versus actual engine temperature (use infrared thermometer for comparison). For used machines, always inspect the entire engine harness for insulation wear, particularly where it routes over the engine block and near hydraulic lines where vibration causes abrasion.

Disclaimer: This guide provides general troubleshooting information for Code D013. Always consult the official Kobelco service manual for your specific machine serial number and seek professional diagnostic assistance if unfamiliar with electrical systems or diagnostic procedures.