Sumitomo SH240-6 Fault Code 112: Complete Diagnostic Guide

What is Sumitomo SH240-6 Fault Code 112?

Fault Code 112 on the Sumitomo SH240-6 excavator indicates an Engine Coolant Temperature (ECT) Sensor Circuit Low Voltage condition. This diagnostic trouble code is triggered when the Engine Control Module (ECM) detects an abnormally low voltage signal from the coolant temperature sensor circuit, typically below 0.2 volts.

The ECT sensor plays a critical role in engine management by monitoring coolant temperature and sending voltage signals to the ECM. This data directly influences fuel injection timing, idle speed control, and fan engagement. On used SH240-6 machines, this code can lead to improper engine performance, increased fuel consumption, and potential overheating if not addressed promptly.

Common Symptoms

When Code 112 is active on your Sumitomo SH240-6, operators typically experience:

• Check Engine Light or malfunction indicator illuminated on the instrument panel
• Hard starting conditions, especially in cold weather, due to incorrect fuel delivery calculations
• Rough idle or engine hunting at low RPM as the ECM compensates for missing temperature data
• Cooling fan running continuously at full speed, regardless of actual engine temperature
• Reduced engine power or derate mode activation in some cases to protect the engine

Potential Causes

For used Sumitomo SH240-6 excavators, Code 112 commonly results from:

• Damaged or shorted ECT sensor wiring harness, particularly at flex points near the engine block where vibration causes insulation wear
• Corroded or loose electrical connectors at the sensor or ECM terminals—common in machines with high hour counts or exposure to moisture
• Failed coolant temperature sensor with internal short circuit to ground
• Contaminated sensor threads with coolant leaks causing electrical grounding issues
• ECM internal fault (rare, but possible in older machines with 8,000+ operating hours)

How to Troubleshoot and Fix Code 112

Step 1: Visual Inspection Begin by inspecting the ECT sensor connector located on the engine block near the thermostat housing. Check for corrosion, moisture intrusion, or damaged pins. On used excavators, examine the entire wiring harness for abrasion points, particularly where it contacts metal surfaces or routing brackets.

Step 2: Electrical Testing Using a digital multimeter, disconnect the ECT sensor and measure resistance across the sensor terminals. A functional sensor typically reads 2,000-3,000 ohms at room temperature. Next, check for continuity to ground—any reading below infinite resistance indicates a shorted sensor requiring replacement.

Step 3: Circuit Verification With the sensor disconnected, measure voltage at the harness connector from the ECM. You should see approximately 5 volts reference voltage. If voltage is absent, trace the wiring back to the ECM for breaks or shorts. Pay special attention to connector terminals for bent pins or corrosion—clean with electrical contact cleaner if needed.

Step 4: Component Replacement If testing confirms sensor failure, replace with a genuine Sumitomo or OEM-equivalent ECT sensor. Apply anti-seize compound to threads and torque to specification (typically 15-20 ft-lbs). Clear the fault code using diagnostic software and verify proper operation.

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Disclaimer: This guide provides general diagnostic information. Always consult the official Sumitomo service manual and consider professional technician assistance for complex electrical issues, especially on used machinery with unknown service history.