What is Sumitomo SH350HD-6 Fault Code 101?

Fault Code 101 on the Sumitomo SH350HD-6 excavator indicates an Engine Coolant Temperature (ECT) Sensor Circuit malfunction or abnormal signal voltage. This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) detects a voltage reading outside the acceptable range from the coolant temperature sensor circuit, typically below 0.2V or above 4.8V on the 5-volt reference circuit.

The ECT sensor plays a critical role in the SH350HD-6's engine management system by monitoring coolant temperature and providing real-time data to the ECM. This information directly affects fuel injection timing, idle speed control, and engine protection protocols. When Code 101 appears, the ECM may default to a preset temperature value, potentially causing inefficient combustion, increased emissions, and compromised engine protection on this heavy-duty excavator model.

Common Symptoms

• Check Engine Light or malfunction indicator lamp illuminated on the instrument cluster
• Engine running rough or hunting at idle, especially during cold starts
• Reduced engine power or failure to reach optimal operating temperature
• Cooling fan running continuously at high speed regardless of actual engine temperature
• Difficulty starting the engine in cold weather conditions due to improper fuel enrichment

Potential Causes

The most common causes of Code 101 on used SH350HD-6 excavators include:

• Faulty ECT sensor due to internal resistance drift or element failure (common after 5,000+ operating hours)
• Damaged wiring harness or corroded connectors, particularly where the harness passes near the engine block or exhaust manifold
• Open or short circuit in the sensor signal wire or ground wire
• Contaminated coolant causing sensor element coating and inaccurate readings
• ECM internal fault (less common) affecting the 5-volt reference circuit
• Loose or corroded ground connections at the engine block mounting point

How to Troubleshoot and Fix Code 101

Step 1: Visual Inspection Begin by inspecting the ECT sensor connector located near the thermostat housing on the engine block. Check for corrosion, moisture intrusion, bent pins, or damaged seals. On used excavators, examine the entire wiring harness for chafing, heat damage, or oil contamination—common issues where harnesses contact frame members.

Step 2: Electrical Testing Disconnect the ECT sensor connector. Using a digital multimeter, measure resistance across the sensor terminals. At 68°F (20°C), resistance should read approximately 2,000-3,000 ohms (consult service manual for exact specifications). Test the signal wire voltage at the harness connector with ignition on, engine off—you should see approximately 5 volts from the ECM reference circuit.

Step 3: Circuit Continuity and Ground Testing Check continuity between the sensor ground wire and chassis ground (should read less than 1 ohm). Inspect for voltage drop in ground circuits. Test signal wire continuity back to the ECM connector to identify breaks or high-resistance connections.

Step 4: Component Replacement If sensor resistance is out of specification or wiring tests reveal faults, replace the defective component. For used machines, always apply dielectric grease to connectors during reassembly to prevent future corrosion. Clear codes using diagnostic software and perform a test cycle to verify repair.

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