Sumitomo SH260LC-6 Fault Code 238: Complete Diagnostic Guide

What is Sumitomo SH260LC-6 Fault Code 238?

Fault Code 238 on the Sumitomo SH260LC-6 excavator indicates a malfunction in the engine coolant temperature sensor circuit or an abnormal temperature reading detected by the Engine Control Module (ECM). This code specifically relates to the coolant temperature sensor sending voltage signals outside the manufacturer's predetermined parameters, typically indicating either a short circuit, open circuit, or sensor degradation.

The coolant temperature sensor is critical for the SH260LC-6's engine management system because it directly influences fuel injection timing, idle speed control, and engine protection protocols. When this sensor fails or provides inaccurate data, the ECM cannot properly regulate engine performance, potentially leading to inefficient combustion, increased emissions, or catastrophic overheating damage. For used excavators, this sensor circuit is particularly vulnerable due to heat cycling, vibration stress, and connector corrosion accumulated over thousands of operating hours.

Common Symptoms

When Code 238 is active on your SH260LC-6, operators typically experience:

• Engine warning light illuminated on the instrument panel, often amber or red depending on severity
• Hard starting conditions or extended cranking time, especially when the engine is cold
• Rough idle or irregular RPM fluctuations during warm-up periods
• Reduced engine power or failure to reach normal operating temperature
• Cooling fan running continuously at maximum speed regardless of actual engine temperature

Potential Causes

The most common technical reasons for Code 238 on used SH260LC-6 excavators include:

• Faulty coolant temperature sensor with internal resistance drift (common after 5,000+ hours)
• Damaged wiring harness near the engine block where vibration causes insulation wear and wire exposure
• Corroded or loose connector pins at the sensor plug, especially in machines exposed to moisture
• ECM internal fault affecting the temperature sensor input circuit (rare but possible in high-hour machines)
• Coolant contamination causing sensor element coating or deterioration
• Ground circuit failure creating intermittent open circuit conditions

How to Troubleshoot and Fix Code 238

Step 1: Visual Inspection Begin by locating the coolant temperature sensor (typically mounted on the engine block near the thermostat housing). Inspect the wiring harness from the sensor to the ECM for obvious damage, chafing against brackets, or heat damage. On used excavators, pay special attention to harness routing points where cable ties may have degraded, allowing wire movement and insulation wear.

Step 2: Electrical Testing Disconnect the sensor and measure resistance across its terminals using a digital multimeter. At 68°F (20°C), resistance should typically read between 2,000-3,000 ohms (consult your service manual for exact specifications). Test the harness connector for corrosion and measure voltage supply from the ECM—you should see approximately 5 volts reference voltage with the key on, engine off.

Step 3: Circuit Verification Check for short circuits by measuring resistance between each sensor wire and ground with the harness disconnected at both ends. Infinite resistance indicates proper insulation. Verify ground integrity by testing continuity between the sensor ground terminal and battery negative.

Step 4: Component Replacement If sensor resistance is out of specification or harness damage is found, replace the defective component. For used machines, always apply dielectric grease to connector pins before reassembly to prevent future corrosion. Clear codes using Sumitomo diagnostic software or compatible scan tool and verify repair with a test cycle.

Disclaimer: This guide provides general diagnostic procedures. Always consult the Sumitomo SH260LC-6 service manual for exact specifications and safety procedures. If unfamiliar with electrical diagnostics, consult a certified heavy equipment technician to prevent further damage.