What is Sumitomo SH200-5 Fault Code 0335?

Fault Code 0335 on the Sumitomo SH200-5 excavator indicates a malfunction in the engine coolant temperature sensor circuit, specifically detecting an abnormally high voltage signal or open circuit condition. This code is triggered when the Engine Control Module (ECM) receives a voltage reading outside the acceptable range from the coolant temperature sensor, typically above 4.5 volts on this system.

The coolant temperature sensor plays a critical role in the SH200-5's Isuzu diesel engine management system. It directly influences fuel injection timing, engine warm-up protocols, and cooling fan engagement. When this sensor fails or its circuit is compromised, the ECM cannot properly regulate engine temperature, potentially leading to inefficient combustion, increased emissions, and accelerated engine wear in used machines already operating under demanding conditions.

Common Symptoms

When Code 0335 is active on your SH200-5, you may experience:

• Engine warning light illuminated on the instrument cluster, often accompanied by audible alerts
• Difficulty starting the engine, especially during cold weather conditions, as the ECM defaults to cold-start parameters
• Cooling fan running continuously at maximum speed, regardless of actual engine temperature
• Poor fuel economy and black smoke from exhaust due to incorrect fuel mapping
• Engine performance derate or reduced power output as a protective measure

Potential Causes

Several factors can trigger Code 0335, particularly in used excavators:

• Damaged or corroded wiring harness at connector points, especially where the harness routes near the engine block (common wear point on older SH200-5 models)
• Failed coolant temperature sensor due to age-related deterioration or coolant contamination
• Open circuit caused by broken wires inside the protective sheathing, often from vibration or heat exposure
• Poor ground connection at the sensor or ECM grounding points
• Coolant intrusion into the sensor connector, causing corrosion and high resistance
• ECM internal fault (rare, but possible in high-hour machines)

How to Troubleshoot and Fix Code 0335

Step 1: Visual Inspection Begin by locating the coolant temperature sensor on the engine block (typically near the thermostat housing on Isuzu engines). Inspect the wiring harness and connector for obvious damage, corrosion, bent pins, or coolant residue. On used excavators, pay special attention to harness routing where it contacts metal surfaces—this is a common failure point.

Step 2: Electrical Testing Disconnect the sensor connector and use a digital multimeter to measure resistance across the sensor terminals. At room temperature (68°F/20°C), resistance should read approximately 2,000-3,000 ohms (verify exact specifications in your service manual). Check for continuity in the wiring from the sensor connector back to the ECM pins, and verify less than 1 ohm of resistance.

Step 3: Voltage Circuit Check With the ignition on but engine off, backprobe the sensor connector and measure the reference voltage from the ECM—it should read approximately 5 volts. If voltage is absent or incorrect, trace the circuit for breaks or test the ECM output. Check the ground circuit resistance to chassis ground (should be less than 0.5 ohms).

Step 4: Component Replacement If testing confirms sensor failure, replace the coolant temperature sensor with an OEM or quality aftermarket unit. On used machines, always replace the connector pigtail simultaneously if any corrosion is present—this prevents recurring failures. Clear codes using diagnostic software and verify repair during a complete heat cycle.

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Disclaimer: This guide provides general troubleshooting information for Code 0335. Always consult the official Sumitomo service manual for your specific machine serial number and consult a certified heavy equipment technician for complex electrical diagnostics or if you're unfamiliar with high-voltage systems.