What is Sumitomo SH210-6 Fault Code 340?

Fault Code 340 on the Sumitomo SH210-6 excavator indicates a malfunction in the hydraulic oil temperature sensor circuit or an abnormal oil temperature reading. This diagnostic trouble code (DTC) is triggered when the machine's Electronic Control Module (ECM) detects either an electrical fault in the sensor wiring or a sensor output that falls outside the acceptable operating parameters.

The hydraulic oil temperature sensor plays a critical role in the SH210-6's performance management system. This sensor continuously monitors the temperature of the hydraulic fluid and sends voltage signals to the ECM. When hydraulic oil temperatures exceed safe operating limits or the sensor circuit malfunctions, the ECM logs Code 340 to prevent potential damage to hydraulic pumps, motors, and seals. For used excavators, this code is particularly important as overheating can accelerate wear on already-aged hydraulic components.

Common Symptoms

When Code 340 is active on your Sumitomo SH210-6, you may experience:

• Hydraulic system warning light illuminated on the instrument panel
• Reduced hydraulic performance or sluggish boom/arm/bucket movements as the system enters derate mode
• Intermittent or continuous alarm beeping from the cab warning system
• Erratic temperature gauge readings on the monitor display, showing unrealistic values
• Automatic engine speed reduction when the ECM attempts to protect the hydraulic system

Potential Causes

Several technical issues can trigger Code 340 on used SH210-6 excavators:

• Faulty hydraulic oil temperature sensor due to internal component degradation or contamination exposure
• Damaged or corroded wiring harness between the sensor and ECM, especially at connector points near the hydraulic tank
• Broken or frayed sensor wires caused by vibration wear or rubbing against the chassis (common failure point on machines with 5,000+ hours)
• Poor electrical connections at the sensor connector due to moisture intrusion or corrosion buildup
• Actual hydraulic oil overheating from insufficient cooling, low oil levels, or clogged hydraulic cooler fins
• ECM internal fault (rare) affecting the sensor input circuit

How to Troubleshoot and Fix Code 340

Step 1: Visual Inspection Begin by locating the hydraulic oil temperature sensor (typically mounted on or near the hydraulic oil tank). Inspect the sensor body for physical damage, oil leaks, or contamination. Check the wiring harness from the sensor to the ECM for obvious damage, abraded insulation, or areas where wires contact metal edges—a common issue in used excavators with worn protective loom.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor connector and measure the resistance across the sensor terminals. Compare your reading against Sumitomo specifications (typically 200-400 ohms at room temperature, varying with temperature). Also check for continuity in the wiring harness and verify there's no short to ground. Inspect connector pins for corrosion or bent terminals, which frequently cause intermittent faults in older machines.

Step 3: Monitor Actual Oil Temperature Use an infrared thermometer to verify actual hydraulic oil temperature against the sensor reading displayed on your diagnostic tool or monitor. If there's significant discrepancy (more than 10°C), the sensor likely requires replacement. For used excavators, also check if the hydraulic oil cooler is functioning properly and oil levels are correct.

Step 4: Component Replacement and Verification If testing confirms sensor failure, replace with a genuine Sumitomo or OEM-equivalent sensor. Clean all connector contacts with electrical contact cleaner before reassembly. After replacement, clear the fault code using Sumitomo diagnostic software or a compatible scanner and operate the machine through a full warm-up cycle to verify the repair.

---

Disclaimer: This guide provides general troubleshooting information for Code 340. Hydraulic and electrical systems can be complex, and improper repairs may cause further damage. Always consult your Sumitomo service manual and consider professional diagnostic assistance for persistent issues or if you're unfamiliar with excavator electrical systems.