What is Sumitomo SH350HD-5 Fault Code 193?

Fault Code 193 on the Sumitomo SH350HD-5 excavator indicates a malfunction in the engine coolant temperature sensor circuit or an abnormal coolant temperature reading. This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) detects voltage signals outside the expected range from the coolant temperature sensor, or when the sensor reports temperature values that are physically impossible or inconsistent with engine operation.

This code is critical for the SH350HD-5 because the coolant temperature sensor provides essential data that the ECM uses to control fuel injection timing, engine warm-up cycles, and protective shutdown protocols. When Code 193 is active, the excavator may enter a derate mode to prevent potential engine damage from overheating or operate with reduced efficiency due to improper fuel mapping.

Common Symptoms

When Fault Code 193 is active on your Sumitomo SH350HD-5, you may experience:

• Check engine warning light or malfunction indicator lamp illuminated on the instrument cluster
• Engine running in limp mode with reduced power output and limited RPM range
• Hard starting conditions, especially during cold weather, or prolonged cranking times
• Erratic temperature gauge readings that fluctuate abnormally or show implausible values (e.g., cold reading when engine is hot)
• Excessive black smoke from the exhaust due to improper fuel-to-air mixture from incorrect temperature compensation

Potential Causes

The most common technical reasons for Code 193 on used SH350HD-5 excavators include:

• Faulty coolant temperature sensor due to internal element degradation or contamination from coolant additives
• Damaged wiring harness or connector corrosion at the sensor plug, particularly where the harness routes near hot exhaust components or sharp metal edges
• Open or short circuit in the sensor wiring caused by vibration-induced wire breakage common in high-hour machines
• Poor ground connection at the ECM or sensor mounting point due to rust or paint buildup
• Contaminated coolant affecting sensor accuracy, or low coolant level exposing the sensor element to air
• ECM calibration issues or internal ECM fault (less common but possible in older units)

How to Troubleshoot and Fix Code 193

Step 1: Visual Inspection Begin by inspecting the coolant temperature sensor located on the engine block near the thermostat housing. Check the electrical connector for corrosion, moisture intrusion, or damaged pins. On used excavators, pay special attention to harness wear points where cables contact the frame or routing brackets. Verify coolant level is adequate and check for visible coolant leaks around the sensor.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure its resistance at various temperatures. A typical coolant temperature sensor shows approximately 2,000-3,000 ohms at room temperature, decreasing as temperature rises. Compare readings to Sumitomo specifications. Next, check continuity in the wiring harness from the sensor connector back to the ECM. Measure for voltage supply at the sensor connector with the key on (typically 5V reference voltage from the ECM).

Step 3: Advanced Diagnostics Connect Sumitomo diagnostic software or a compatible scan tool to monitor live coolant temperature data. Compare the sensor reading to actual engine temperature using an infrared thermometer on the engine block. If readings differ by more than 10°F, replace the sensor. For used machines, inspect the sensor mounting threads for thread sealant buildup that can insulate the sensor and cause false readings.

Step 4: Repair and Verification Replace the faulty component (sensor, harness, or connector). When installing a new coolant temperature sensor, apply appropriate thread sealant and torque to specification (typically 15-20 ft-lbs). Clear the fault code using diagnostic software and perform a test run, monitoring coolant temperature through several heat cycles to confirm proper operation.

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Disclaimer: This guide provides general troubleshooting information for Sumitomo SH350HD-5 excavators. Always consult the manufacturer's service manual for model-specific procedures and specifications. If you're uncomfortable performing these diagnostics or if the problem persists, contact a certified Sumitomo technician or qualified heavy equipment mechanic for professional assistance.