Sumitomo SH200-5 Fault Code 1112: Complete Diagnostic Guide

What is Sumitomo SH200-5 Fault Code 1112?

Fault Code 1112 on the Sumitomo SH200-5 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 open circuit, short circuit, or out-of-range signal from the coolant temperature sensor.

This fault is critical for the SH200-5 because the coolant temperature sensor directly influences fuel injection timing, engine warm-up protocols, and hydraulic oil temperature management. When the ECM cannot accurately monitor engine temperature, it may trigger protective derate modes or prevent the machine from reaching optimal operating efficiency, significantly impacting productivity on job sites.

Common Symptoms

Operators and mechanics typically observe these issues when Code 1112 is active:

• Warning light illumination on the instrument cluster, often accompanied by a continuous or intermittent audible alarm
• Reduced engine power or derate mode activation, limiting hydraulic system performance and swing/boom speed
• Difficulty starting the engine, particularly in cold weather conditions, as the ECM defaults to safe-mode fuel maps
• Erratic temperature gauge readings that fluctuate unrealistically or remain stuck at minimum/maximum positions
• Increased fuel consumption due to the ECM running rich fuel mixtures as a protective measure

Potential Causes

For used SH200-5 excavators, these are the most common underlying issues:

• Corroded or damaged sensor connector at the coolant temperature sensor mounting location (common failure point after 5,000+ operating hours)
• Failed coolant temperature sensor due to thermal cycling stress or internal component degradation
• Damaged wiring harness between the sensor and ECM, particularly where the harness routes near the engine block or experiences vibration
• Poor ground connection at the sensor circuit, often caused by corrosion on chassis ground points
• ECM internal fault (less common) affecting the sensor input circuitry
• Low coolant level creating air pockets that prevent accurate temperature sensing

How to Troubleshoot and Fix Code 1112

Step 1: Visual Inspection Begin by inspecting the coolant temperature sensor connector for corrosion, oil contamination, or physical damage. On used excavators, check for harness wear at known friction points near engine mounts and valve covers. Verify coolant level is correct—air in the system can cause intermittent readings.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure its resistance at various temperatures (typically 2,000-3,000 ohms at 68°F/20°C). Compare readings against Sumitomo specifications. Check for continuity in the wiring harness from sensor to ECM connector (Pin identification required from service manual). Test for voltage supply at the sensor connector—should read approximately 5 volts with ignition on.

Step 3: Component Replacement and Verification If resistance values are incorrect or wiring shows damage, replace the coolant temperature sensor (genuine Sumitomo or OEM-equivalent parts recommended). For used machines, always apply dielectric grease to connectors during reassembly to prevent future corrosion. Clear codes using diagnostic software compatible with Sumitomo systems and monitor during a complete warm-up cycle.

Disclaimer: This guide provides general troubleshooting information. Always consult the official Sumitomo service manual for your specific machine serial number and seek professional diagnosis for complex electrical issues or if safety systems are involved.