Sumitomo SH300-6 Fault Code 117: Complete Diagnostic Guide

What is Sumitomo SH300-6 Fault Code 117?

Fault Code 117 on the Sumitomo SH300-6 excavator indicates a malfunction in the engine coolant temperature sensor circuit, specifically detecting an abnormally high voltage signal or open circuit condition in the ECM (Engine Control Module) input.

This diagnostic trouble code triggers when the engine control system detects a voltage reading outside the normal operating range (typically above 4.5-4.8 volts) from the coolant temperature sensor. The SH300-6's Isuzu engine relies heavily on accurate temperature data to manage fuel injection timing, idle speed control, and engine protection protocols. When this sensor circuit fails, the ECM cannot properly monitor engine thermal conditions, potentially leading to overheating damage or improper fuel delivery that reduces machine efficiency and increases operational costs.

Common Symptoms

When Code 117 is active on your SH300-6, operators typically experience:

• Check Engine Light or malfunction indicator illuminated on the instrument cluster
• Engine running in limp mode with reduced power output (derate) to prevent potential damage
• Erratic idle speed or rough running, especially during cold starts
• Cooling fan running continuously at high speed as the ECM defaults to maximum cooling
• Inaccurate temperature gauge readings showing extreme high or low values inconsistently

Potential Causes

The most common technical failures triggering Code 117 on used SH300-6 excavators include:

• Open circuit or damaged wiring in the sensor harness, particularly where cables route near the engine block and experience heat cycling
• Corroded or loose connector pins at the coolant temperature sensor or ECM connections
• Failed coolant temperature sensor (NTC thermistor type) due to internal element breakage
• Chafed wiring harness at common rub points near engine mounts or valve covers
• Low coolant levels causing sensor exposure to air instead of coolant
• ECM internal circuit failure (rare, but possible in high-hour machines)

How to Troubleshoot and Fix Code 117

Step 1: Visual Inspection Begin by inspecting the coolant temperature sensor located on the engine block (typically near the thermostat housing on Isuzu engines). Check the electrical connector for corrosion, bent pins, or moisture intrusion. On used excavators, examine the entire wiring harness from sensor to ECM for signs of abrasion, melting, or damage from rubbing against engine components.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure resistance across the sensor terminals. At 68°F (20°C), resistance should typically read 2,000-3,000 ohms (consult service manual for exact specifications). Check for continuity in the wiring harness between the sensor connector and ECM. Measure voltage supply from the ECM—you should see approximately 5 volts reference voltage with the sensor disconnected.

Step 3: Component Replacement and Verification If resistance values are out of specification or the harness shows open circuit, replace the faulty component. For used machines, always apply dielectric grease to connectors during reassembly to prevent future corrosion. After repairs, clear the fault code using Sumitomo diagnostic software or a compatible scan tool, then run the engine through temperature cycles to verify the repair. Monitor live data to confirm the ECM receives proper temperature signals (voltage should decrease as temperature rises).

Disclaimer: This guide provides general troubleshooting information. Always consult the official Sumitomo service manual for your specific serial number and consider professional diagnostic assistance for complex electrical issues or if you're unfamiliar with high-voltage systems.