Sumitomo SH300-6 Fault Code 112: Complete Diagnostic Guide

What is Sumitomo SH300-6 Fault Code 112?

Fault Code 112 on the Sumitomo SH300-6 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 relates to the coolant temperature sensor sending irregular voltage signals outside the expected range to the ECM, preventing accurate engine temperature monitoring.

The coolant temperature sensor plays a critical role in engine protection and performance optimization on the SH300-6. The ECM uses this data to adjust fuel injection timing, control engine warm-up cycles, and trigger protective shutdown sequences if overheating occurs. When Code 112 activates, the engine management system cannot reliably monitor thermal conditions, potentially leading to component damage or reduced operational efficiency.

Common Symptoms

When Fault Code 112 is active on your Sumitomo SH300-6, you may experience:

• Engine warning light illuminated on the instrument cluster, often accompanied by a temperature alert icon
• Hard starting conditions or rough idle, especially when the engine is cold
• Cooling fan running continuously at high speed regardless of actual engine temperature
• Reduced engine power or derate mode activation as a protective measure
• Inaccurate temperature gauge readings showing extremely high or low temperatures that don't match actual conditions

Potential Causes

The most common technical causes for Code 112 on used SH300-6 excavators include:

• Faulty coolant temperature sensor due to internal resistance drift or element failure (common after 5,000+ operating hours)
• Damaged or corroded wiring harness connecting the sensor to the ECM, particularly at connector pins exposed to coolant leaks
• Broken or shorted sensor wiring near the engine block where harness routing causes friction wear against metal surfaces
• Poor electrical ground connection at the sensor mounting point due to corrosion or loose hardware
• Contaminated coolant causing sensor element coating or degradation
• ECM internal fault (rare, but possible in high-hour machines with electrical system stress)

How to Troubleshoot and Fix Code 112

Step 1: Visual Inspection Begin by inspecting the coolant temperature sensor location on the engine block. Check for coolant leaks around the sensor threads, corrosion on the electrical connector, and physical damage to the wiring harness. On used excavators, pay special attention to wire chafing points where the harness contacts the engine or frame components.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor connector and measure resistance across the sensor terminals at different temperatures. A cold sensor (68°F/20°C) should typically read 2,000-3,000 ohms, while a warm sensor (176°F/80°C) should read 200-400 ohms. Consult your service manual for exact specifications. Also check for continuity in the wiring from sensor to ECM and verify ground circuit integrity.

Step 3: Connector and Harness Inspection Carefully examine the sensor connector pins for corrosion, bent terminals, or moisture intrusion. Clean contacts with electrical contact cleaner and apply dielectric grease. Inspect the entire harness for insulation breaks or signs of heat damage, particularly common on machines operating in extreme conditions.

Step 4: Sensor Replacement and Verification If testing confirms sensor failure, replace with an OEM or equivalent quality sensor. Apply thread sealant rated for coolant contact and torque to specification. Clear fault codes using diagnostic software compatible with Sumitomo systems, then monitor for code recurrence during a complete warm-up cycle.

Disclaimer: This guide provides general diagnostic information. Complex electrical issues or repeated code occurrences should be evaluated by a certified Sumitomo technician with access to manufacturer-specific diagnostic equipment and service bulletins for your machine's serial number range.