Sumitomo SH220LC-5 Fault Code 1112: Complete Diagnostic Guide

What is Sumitomo SH220LC-5 Fault Code 1112?

Fault Code 1112 on the Sumitomo SH220LC-5 indicates a malfunction in the engine coolant temperature sensor circuit or an out-of-range coolant temperature reading. This code is triggered when the Electronic Control Module (ECM) detects an abnormal voltage signal from the coolant temperature sensor, typically indicating either an open circuit, short circuit, or sensor failure.

The coolant temperature sensor is critical for the SH220LC-5's Isuzu engine management system. It directly influences fuel injection timing, engine warm-up cycles, and prevents overheating damage. When this sensor fails, the ECM defaults to a predetermined temperature value, which can lead to poor fuel economy, hard starting in cold conditions, and potential engine damage from undetected overheating.

Common Symptoms

When Code 1112 is active on your SH220LC-5, operators typically experience:

• Engine warning light illuminated on the instrument cluster, often with a temperature-related indicator
• Hard starting or extended cranking time, especially in cold weather conditions
• Black smoke from the exhaust due to improper fuel-air mixture calculations
• Poor engine performance or rough idling during warm-up phase
• Cooling fan running continuously at high speed, regardless of actual engine temperature

Potential Causes

In used Sumitomo SH220LC-5 excavators, Code 1112 typically results from:

• Faulty coolant temperature sensor – the sensor element deteriorates over time, especially in machines with 5,000+ operating hours
• Damaged wiring harness – common rub points exist where the harness passes near the engine block or crosses sharp metal edges
• Corroded or loose electrical connectors – moisture intrusion at the sensor connector causes intermittent signals
• ECM internal fault – less common, but possible in older machines with voltage spike history
• Coolant contamination affecting sensor accuracy – glycol breakdown or oil contamination from head gasket issues

How to Troubleshoot and Fix Code 1112

Step 1: Visual Inspection Begin by locating the coolant temperature sensor on the engine block (typically near the thermostat housing on Isuzu engines). Inspect the wiring harness for obvious damage, chafing, or burns. Check the connector for corrosion, bent pins, or moisture. On used excavators, pay special attention to harness routing near hot exhaust components.

Step 2: Electrical Testing Disconnect the sensor connector and use a digital multimeter to measure resistance across the sensor terminals. At 68°F (20°C), resistance should be approximately 2,000-3,000 ohms (consult your service manual for exact specifications). Test the harness continuity from the sensor connector back to the ECM – you should see less than 5 ohms resistance and no continuity to ground.

Step 3: Voltage Signal Check With the ignition on and sensor connected, back-probe the signal wire at the connector. You should see approximately 5 volts reference voltage from the ECM. If voltage is absent, suspect ECM issues or harness damage. If present but the code persists after sensor replacement, check for intermittent shorts caused by harness movement during machine operation.

Step 4: Sensor Replacement and Verification Replace the coolant temperature sensor using OEM or high-quality aftermarket parts. Apply dielectric grease to connector terminals before reconnecting. Clear the fault code using diagnostic software (Sumitomo SH-TESTER or compatible J1939 scanner) and operate the machine through a complete heat cycle to verify the repair.

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Disclaimer: This guide provides general troubleshooting information for Sumitomo SH220LC-5 excavators. Always consult the manufacturer's service manual and consider professional diagnostic assistance for complex electrical issues. Improper repairs may cause additional damage or safety hazards.