What is Sumitomo SH350HD-5 Fault Code 1345?

Fault Code 1345 on the Sumitomo SH350HD-5 excavator indicates a malfunction in the hydraulic oil temperature sensor circuit, specifically signaling an abnormal voltage reading or open/short circuit condition. This diagnostic trouble code (DTC) is generated when the Electronic Control Module (ECM) detects that the hydraulic oil temperature sensor is sending values outside the normal operating range (typically 0.5-4.5 volts).

The hydraulic oil temperature sensor plays a critical role in the SH350HD-5's performance management system. It monitors the temperature of the hydraulic fluid circulating through the excavator's working circuits, pumps, and motors. When hydraulic oil exceeds safe operating temperatures (usually above 80-90°C), the ECM relies on this sensor data to trigger warning systems or initiate protective derate modes. For used excavators, this sensor and its wiring harness are particularly vulnerable to degradation from years of heat cycling, vibration, and exposure to contaminated hydraulic fluid.

Common Symptoms

When Code 1345 is active on your SH350HD-5, operators typically experience:

• Hydraulic oil temperature warning light illuminated on the instrument cluster (often amber or red)
• Reduced hydraulic system performance or automatic engine derate to protect components from overheating
• Inaccurate or erratic temperature gauge readings on the monitor display (showing extremely high or low readings that don't match actual conditions)
• Intermittent alarm beeping in the cab, especially during warm-up or high-load operations
• ECM logging the fault even when hydraulic oil feels cool to the touch (indicating sensor failure rather than actual overheating)

Potential Causes

The most common technical causes for Code 1345 on used SH350HD-5 excavators include:

• Faulty hydraulic oil temperature sensor due to internal element degradation or contamination from metallic debris in aged hydraulic fluid
• Damaged or corroded wiring harness at the sensor connector, particularly where the harness routes near the hydraulic tank or hot engine components
• Chafed or pinched sensor wiring at known rub points along the main boom or near the hydraulic pump mounting area
• Corroded or loose electrical connectors at the sensor plug or ECM connection points (common in machines with 5,000+ operating hours)
• ECM internal fault or software glitch (rare, but possible in older control modules)
• Poor ground connection in the sensor circuit causing voltage irregularities

How to Troubleshoot and Fix Code 1345

Step 1: Visual Inspection and Connector Check

Begin by locating the hydraulic oil temperature sensor, typically mounted on the hydraulic oil tank or return line manifold. Disconnect the sensor's electrical connector and inspect both the male and female terminals for corrosion, bent pins, or oil contamination. On used excavators, these connectors often accumulate moisture and debris. Clean contacts with electrical contact cleaner and apply dielectric grease before reconnection. Trace the wiring harness back toward the ECM, looking for obvious damage, chafing against metal edges, or areas where harness ties have failed.

Step 2: Electrical Testing with Multimeter

Using a digital multimeter (DMM), measure the sensor's resistance with the connector disconnected and engine cold. A functional sensor typically reads 2,000-3,000 ohms at 20°C (consult your service manual for exact specifications). Next, check for continuity in the wiring harness from the sensor connector back to the ECM pins. Measure voltage supply at the sensor connector with ignition on (should read approximately 5 volts on the signal wire). If voltage is absent or incorrect, suspect ECM issues or harness breaks. Also verify a solid ground circuit with less than 1 ohm resistance.

Step 3: Sensor Replacement and System Verification

If electrical tests confirm sensor failure, replace the hydraulic oil temperature sensor with a genuine Sumitomo or OEM-equivalent part (aftermarket sensors often cause recurring codes on used machines). Before installing, check that the sensor mounting boss is clean and threads are undamaged. After replacement, clear the fault code using Sumitomo diagnostic software or a compatible scanner tool. Run the machine through a complete warm-up cycle while monitoring live data to confirm the new sensor provides accurate temperature readings (gradually climbing from ambient to 60-80°C under normal operation). For used excavators with over 8,000 hours, consider replacing the entire sensor harness segment if wiring shows heat damage or brittleness.

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Disclaimer: This guide provides general troubleshooting information for Code 1345. Hydraulic and electrical system repairs should be performed by qualified technicians with proper training and tools. Always consult the official Sumitomo service manual for your specific machine serial number and follow all safety protocols when working on heavy equipment.