What is Kobelco SK350LC-8 Fault Code D022?

Kobelco SK350LC-8 fault code D022 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, typically indicating an open circuit, short circuit, or sensor reading outside the expected parameters.

The coolant temperature sensor is critical for the SK350LC-8's Hino J05E engine management system. This sensor provides real-time temperature data that the ECM uses to adjust fuel injection timing, control engine warm-up enrichment, activate cooling fans, and protect the engine from overheating. When code D022 is active, the ECM often defaults to a pre-programmed "limp mode" value, which can negatively impact engine performance, fuel efficiency, and emissions control.

Common Symptoms

When fault code D022 is active on your Kobelco SK350LC-8, you may experience:

• Engine warning light illuminated on the instrument cluster, possibly accompanied by a specific coolant temperature warning icon
• Hard starting or extended cranking, especially when the engine is cold, due to improper fuel enrichment
• Poor engine performance including rough idle, hesitation, or reduced power output
• Cooling fan running continuously at high speed, even when the engine is cool
• Increased fuel consumption as the ECM compensates for missing temperature data with conservative fuel mapping

Potential Causes

Several factors commonly trigger code D022 on used SK350LC-8 excavators:

• Failed coolant temperature sensor due to age-related degradation or thermal stress cycles
• Damaged or corroded wiring harness at the sensor connector, particularly where the harness routes near hot exhaust components or sharp metal edges
• Open or short circuit in the sensor signal wire between the sensor and the ECM
• Corroded electrical connectors at the sensor or ECM, especially in machines exposed to harsh environments
• Poor ground connection affecting the sensor's reference voltage
• ECM internal failure (rare, but possible in high-hour machines)

How to Troubleshoot and Fix Code D022

Step 1: Visual Inspection Begin with a thorough visual examination of the coolant temperature sensor located 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 obvious damage, abrasion points where the harness contacts metal surfaces, or melted insulation near heat sources. On used excavators, pay special attention to harness routing—years of vibration can cause wires to rub through protective sheathing.

Step 2: Electrical Testing Using a digital multimeter, disconnect the coolant temperature sensor connector and measure resistance across the sensor terminals. For the Hino J05E engine, resistance should typically read approximately 2,000-3,000 ohms at 68°F (20°C), decreasing as temperature increases. Compare your readings to Kobelco's specification chart. Next, check for continuity in the signal wire from the sensor connector to the ECM connector. Resistance should be less than 5 ohms. Also verify the ground circuit has less than 1 ohm resistance.

Step 3: Voltage and Signal Testing With the ignition on but engine off, check for reference voltage at the sensor connector—you should see approximately 5 volts from the ECM. If reference voltage is absent, suspect ECM issues or harness problems. If voltage is present but the sensor tested faulty, replace the sensor. After repairs, use Kobelco diagnostic software (or compatible aftermarket tools like Jaltest or OEM-level interfaces) to clear the code and monitor live data to confirm proper sensor operation across the full temperature range.

Step 4: Used Equipment Considerations For used excavators, replace the sensor connector if any corrosion or terminal spread is detected—don't just clean it. Inspect the entire engine harness for age-related degradation, especially rubber grommets and protective looms. Consider applying dielectric grease to the new connection to prevent future corrosion.

---

Disclaimer: This guide provides general troubleshooting information for Kobelco SK350LC-8 fault code D022. Always consult the official Kobelco service manual and consider professional diagnostic assistance for complex electrical issues. Improper repairs may cause additional damage or safety hazards.