What is Hitachi ZX350LCK-5G Fault Code 11307-3?

Fault Code 11307-3 indicates a Hydraulic Oil Temperature Sensor Circuit Abnormality (Low Input Voltage) on the Hitachi ZX350LCK-5G excavator. This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) detects voltage readings from the hydraulic oil temperature sensor that fall below the manufacturer's specified threshold, typically under 0.2 volts.

The hydraulic oil temperature sensor plays a critical role in protecting the ZX350LCK-5G's hydraulic system by monitoring oil temperature and preventing overheating conditions. When this sensor circuit fails, the ECM cannot accurately assess hydraulic system health, potentially leading to component damage or reduced performance. This code is particularly important on used excavators where sensor degradation and wiring harness wear are common issues.

Common Symptoms

• Yellow warning lamp illuminated on the instrument cluster with reduced hydraulic performance
• ECM derate mode activated, limiting engine RPM to approximately 1,200-1,400 range to protect hydraulic components
• Hydraulic oil temperature gauge reading abnormally low or displaying dashes/error symbols
• Sluggish hydraulic response during operation, especially during warm-up cycles
• Stored fault code in ECM memory even after apparent normal operation resumes

Potential Causes

The most frequent causes of Code 11307-3 on used ZX350LCK-5G excavators include:

• Open circuit in the sensor wiring harness, commonly occurring where the harness passes near the hydraulic tank mounting bracket (known rub point)
• Failed hydraulic oil temperature sensor due to internal element degradation or moisture intrusion
• Corroded or loose connector pins at the sensor plug or ECM connection points
• Damaged wiring insulation causing short to ground between the sensor and ECM
• Faulty ECM internal circuit (rare, but possible on high-hour machines)
• Poor ground connections at the sensor mounting location due to rust or paint buildup

How to Troubleshoot and Fix Code 11307-3

Step 1: Visual Inspection Locate the hydraulic oil temperature sensor on the left side of the hydraulic tank. Inspect the wiring harness for visible damage, abrasion, or oil contamination. Check the connector for corrosion, bent pins, or moisture. On used excavators, pay special attention to harness routing near sharp edges and moving components.

Step 2: Electrical Testing Disconnect the sensor connector and measure resistance across the sensor terminals using a digital multimeter. At 20°C (68°F), resistance should read approximately 2,200-2,800 ohms. Check continuity from the sensor connector to the ECM connector (consult wiring diagrams). Resistance should be less than 5 ohms; infinite resistance indicates an open circuit.

Step 3: Voltage Supply Check With the ignition on and sensor disconnected, measure voltage at the harness connector. You should see approximately 5 volts supply voltage from the ECM. If voltage is absent, trace the circuit back toward the ECM, checking for breaks or shorts.

Step 4: Ground Circuit Verification Verify the sensor ground circuit has less than 0.5 ohms resistance to chassis ground. Clean the sensor mounting surface and ensure proper metal-to-metal contact for grounding.

Step 5: Component Replacement If electrical tests confirm sensor failure, replace with a genuine Hitachi sensor (Part #4448336 or equivalent). Clear codes using Dr.EX diagnostic software or compatible scan tool and perform a test cycle.

Disclaimer: This guide provides general troubleshooting information. Always consult the Hitachi ZX350LCK-5G service manual and consider professional diagnostic assistance for complex electrical issues. Improper repairs may cause additional system damage.