What is Kobelco SK200-8 Fault Code P0117?

Fault Code P0117 on the Kobelco SK200-8 excavator indicates "Engine Coolant Temperature (ECT) Sensor Circuit Low Input." This diagnostic trouble code is triggered when the engine control module (ECM) detects an abnormally low voltage signal from the coolant temperature sensor, typically below 0.14 volts. The ECT sensor is a critical component that monitors engine coolant temperature and sends this data to the ECM to regulate fuel injection timing, idle speed, and emission controls.

On the SK200-8's Hino J05E diesel engine, accurate coolant temperature readings are essential for optimal performance and preventing engine damage. When this code appears, the ECM may default to a substitute temperature value, leading to improper fuel mapping and potential engine protection modes that limit machine performance.

Common Symptoms

When P0117 is active on your Kobelco SK200-8, you may experience:

• Check Engine Light or warning lamp illuminated on the instrument cluster
• Hard starting, especially in cold conditions, due to incorrect fuel enrichment
• Rough idle or engine running rich (black smoke from exhaust)
• Cooling fan running continuously at high speed
• Reduced engine power or derate mode activation to protect the engine
• Poor fuel economy and increased emissions

Potential Causes

Several factors can trigger P0117 on used excavators, including:

• Defective ECT sensor with internal short circuit or degraded thermistor element
• Damaged or corroded wiring harness between the sensor and ECM (common wear point near engine mounting brackets)
• Shorted sensor signal wire to ground due to harness chafing against engine components
• Corroded or loose electrical connectors at the sensor or ECM terminals
• Failed ECM (rare, but possible on high-hour machines)
• Low coolant level causing sensor exposure to air instead of coolant

How to Troubleshoot and Fix Code P0117

Step 1: Visual Inspection Begin by inspecting the ECT sensor located on the engine block near the thermostat housing. Check for physical damage, coolant leaks, and verify adequate coolant level. On used excavators, carefully examine the entire sensor harness for rubbing points, especially where it routes past the engine mount and fuel lines—a known wear area on the SK200-8.

Step 2: Electrical Testing Disconnect the ECT sensor connector and use a digital multimeter to measure resistance across the sensor terminals. At 68°F (20°C), resistance should read approximately 2,000-3,000 ohms. Test the wiring harness by checking for continuity between the sensor connector and ECM pins, and verify no short to ground exists (resistance should be infinite to ground). Check for voltage supply from the ECM—typically 5 volts reference signal.

Step 3: Component Replacement and Verification If testing reveals a faulty sensor, replace it with a genuine Kobelco or OEM-equivalent part (part number YN52S00015P1). Clean connector terminals with electrical contact cleaner and apply dielectric grease to prevent corrosion. If wiring damage is found, repair or replace the affected harness section with heat-shrink connections. Clear the code using Kobelco diagnostic software or a compatible scanner, then run the engine through temperature cycles to verify the repair.

Disclaimer: This guide provides general troubleshooting information. For complex electrical issues or if you're uncertain about any procedure, consult a certified Kobelco technician or qualified heavy equipment mechanic.