Sumitomo SH220LC-6 Fault Code 1112: Complete Diagnostic Guide

What is Sumitomo SH220LC-6 Fault Code 1112?

Fault Code 1112 on the Sumitomo SH220LC-6 indicates an Engine Speed Sensor (ESS) circuit malfunction or signal error. This code is triggered when the Electronic Control Module (ECM) detects an abnormal voltage reading, intermittent signal, or complete loss of communication from the engine speed sensor circuit.

The engine speed sensor is critical for the SH220LC-6's performance because it provides real-time crankshaft rotational data to the ECM. This information is essential for controlling fuel injection timing, engine load management, and hydraulic system synchronization. When this sensor fails, the excavator's computer cannot properly regulate engine functions, leading to performance degradation or complete shutdown in severe cases.

Common Symptoms

When Code 1112 is active on your Sumitomo SH220LC-6, you may experience:

• Check Engine Light or warning lamp illuminated on the instrument panel
• Engine derating (reduced power output) or engine running in limp mode
• Erratic engine RPM fluctuations or unstable idle conditions
• Difficulty starting the engine, especially when cold
• Hydraulic system performance issues due to improper engine-pump coordination
• Complete engine shutdown in severe sensor failure cases

Potential Causes

The most common technical reasons for Code 1112 on used SH220LC-6 excavators include:

• Damaged or contaminated engine speed sensor due to oil leaks, metal debris, or physical impact
• Worn wiring harness near the sensor mounting location where vibration causes conductor breakage
• Corroded or loose electrical connectors at the sensor plug or ECM interface
• Sensor air gap issues caused by excessive crankshaft runout or incorrect sensor positioning
• Faulty ECM (less common) with damaged input circuits
• Broken reluctor wheel teeth on the crankshaft or flywheel
• Water intrusion into sensor connectors on machines operating in wet conditions

How to Troubleshoot and Fix Code 1112

Step 1: Visual Inspection Begin by locating the engine speed sensor (typically mounted on the engine block near the flywheel housing). Inspect the sensor body for physical damage, cracks, or oil contamination. Check the wiring harness from the sensor to the ECM for signs of rubbing, pinching, or heat damage—common wear points on used excavators include areas near engine mounts and along the frame rail.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure its resistance (typically 200-1000 ohms for most inductive sensors—consult your service manual for exact specifications). Test the harness continuity from the sensor connector to the ECM. Check for voltage supply (usually 5V or 12V reference voltage) at the sensor connector with the key on, engine off.

Step 3: Sensor Air Gap Verification Verify the air gap between the sensor tip and reluctor wheel using a feeler gauge (typical specification: 0.5-1.5mm). On used machines, worn engine mounts can cause excessive crankshaft movement, altering this critical gap.

Step 4: Advanced Diagnostics Connect Sumitomo diagnostic software (or compatible scan tool) to monitor live sensor data. Observe the frequency signal while manually rotating the engine. An intermittent or erratic signal indicates sensor or reluctor wheel problems.

Step 5: Repair or Replace Clean all electrical connectors with contact cleaner and apply dielectric grease. Replace the sensor if resistance values are out of specification. For used excavators, always inspect connector pins for corrosion—a common failure point that's often overlooked before expensive part replacement.

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Disclaimer: This guide provides general troubleshooting information. Always consult your Sumitomo service manual and consider professional diagnosis for complex electrical issues. Improper repairs may cause further damage or safety hazards.