What is Sumitomo SH220LC-6 Fault Code 93?

Fault Code 93 on the Sumitomo SH220LC-6 excavator indicates a malfunction in the engine coolant temperature sensor circuit or an abnormal coolant temperature reading detected by the Engine Control Module (ECM). This code specifically signals that the ECM has identified either an out-of-range voltage signal from the coolant temperature sensor, a short or open circuit in the sensor wiring, or that the actual coolant temperature has exceeded safe operating parameters.

This fault is critical for the SH220LC-6 because the ECM relies on accurate coolant temperature data to manage fuel injection timing, engine protection protocols, and overall thermal management. When this sensor circuit fails, the engine may enter a protective derate mode or fail to start, potentially causing expensive downtime on job sites. For used excavators, this sensor and its wiring harness are particularly vulnerable to corrosion and heat-related degradation over time.

Common Symptoms

• Check Engine light or warning lamp illuminated on the instrument cluster
• Engine fails to reach normal operating temperature or runs excessively hot without proper warning
• Engine enters limp mode with reduced power output to protect internal components
• Difficulty starting the engine, especially in cold weather conditions
• Cooling fan runs continuously at maximum speed regardless of actual engine temperature

Potential Causes

The most common technical causes for Code 93 on used SH220LC-6 excavators include:

• Coolant temperature sensor failure due to age, thermal cycling, or internal element degradation
• Damaged or corroded wiring harness between the sensor and ECM, particularly at connector pins exposed to engine heat and moisture
• Poor ground connection at the sensor mounting point or ECM ground circuit
• Shorted sensor wiring rubbing against engine components or frame (common wear point near the thermostat housing)
• Low coolant level causing inaccurate temperature readings or air pockets near the sensor
• ECM internal fault (less common but possible in high-hour machines)

How to Troubleshoot and Fix Code 93

Step 1: Visual Inspection Begin by inspecting the coolant temperature sensor location (typically near the thermostat housing on the engine block). Check for damaged wiring, corroded connector pins, or evidence of coolant leaks. On used excavators, examine the entire harness route for abrasion points where wires contact hot engine surfaces.

Step 2: Test Sensor Resistance Disconnect the coolant temperature sensor connector. Using a digital multimeter, measure the sensor's resistance. At room temperature (20°C/68°F), resistance should typically read between 2,000-3,000 ohms (consult service manual for exact specifications). Compare readings at different temperatures—resistance should decrease as temperature increases.

Step 3: Check Circuit Voltage With the sensor disconnected and ignition on, measure voltage at the harness connector from the ECM side. You should see approximately 5 volts reference voltage from the ECM. If voltage is absent, trace the wiring for opens or shorts to ground.

Step 4: Inspect Ground Circuit Verify continuity between the sensor ground pin and the ECM ground. Clean all ground connections and sensor mounting threads, as corrosion buildup is extremely common in older machines and creates false readings.

Step 5: Clear Code and Test After repairs, clear the fault code using Sumitomo diagnostic software or a compatible scan tool. Run the engine through a complete heat cycle and monitor for code recurrence.

Disclaimer: This guide provides general troubleshooting information. Always consult the official Sumitomo service manual for your specific machine serial number. If you're uncomfortable performing electrical diagnostics, contact a certified heavy equipment technician to prevent further damage.