What is Hitachi ZW310-5A Fault Code 111705-9?

Fault Code 111705-9 on the Hitachi ZW310-5A wheel loader indicates a malfunction in the hydraulic oil temperature sensor circuit, specifically detecting an abnormally high voltage signal or open circuit condition. This Diagnostic Trouble Code (DTC) is generated by the machine's Electronic Control Module (ECM) when it receives a voltage reading outside the acceptable range from the hydraulic oil temperature sensor, typically above 4.5 volts when the normal operating range should be 0.5-4.5 volts.

This code is critical for the ZW310-5A because the hydraulic system relies on accurate temperature monitoring to prevent overheating, maintain optimal viscosity, and protect expensive hydraulic components. When this sensor fails, the ECM cannot properly manage hydraulic system protection protocols, potentially leading to reduced machine performance or automatic derate modes that limit hydraulic functions.

Common Symptoms

• Dashboard warning light illuminated (typically a yellow hydraulic system indicator or check engine light)
• Reduced hydraulic performance or slower cycle times as the ECM enters protective mode
• Inaccurate temperature gauge readings showing extremely high or no temperature reading
• Intermittent fault occurrence especially during machine startup or when operating in cold conditions
• Stored fault codes in ECM memory even after the warning light clears

Potential Causes

The most common causes for Code 111705-9 on used Hitachi ZW310-5A machines include:

• Damaged or corroded wiring harness connections at the sensor plug, particularly where the harness routes near the hydraulic tank and experiences vibration
• Failed hydraulic oil temperature sensor due to age-related degradation or contamination from hydraulic fluid breakdown
• Open circuit or broken wire in the sensor signal wire, commonly found where harnesses rub against frame components
• Corroded connector pins at the sensor or ECM connection points, especially in machines operated in wet or coastal environments
• ECM internal fault (less common) affecting the sensor input circuit

How to Troubleshoot and Fix Code 111705-9

Step 1: Visual Inspection Begin by locating the hydraulic oil temperature sensor mounted on or near the hydraulic reservoir. Inspect the wiring harness from the sensor to the ECM for obvious damage, chafing, or corrosion. On used excavators, pay particular attention to harness routing points where vibration causes wire insulation wear.

Step 2: Electrical Testing Disconnect the sensor connector and use a digital multimeter to measure resistance across the sensor terminals. A functioning sensor typically reads 2,000-3,000 ohms at room temperature (consult service manual for exact specs). An infinite resistance reading indicates an open sensor requiring replacement.

Step 3: Circuit Verification With the sensor disconnected, check for voltage at the harness connector. You should see approximately 5 volts reference voltage from the ECM. Measure continuity between the sensor ground wire and chassis ground—it should read less than 1 ohm. High resistance here indicates ground circuit problems.

Step 4: Connector Service Clean all connector pins with electrical contact cleaner and inspect for bent pins or corrosion. On used machinery, connector deterioration is frequently overlooked but commonly causes intermittent high-voltage codes.

Step 5: Component Replacement If testing confirms sensor failure, replace with a genuine Hitachi replacement sensor (Part Number specific to ZW310-5A). After installation, clear fault codes using Hitachi diagnostic software or compatible scan tool and verify repair with a test cycle.

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Disclaimer: This guide provides general troubleshooting information. Always consult the official Hitachi service manual for your specific machine serial number and seek professional assistance from certified Hitachi technicians for complex electrical diagnostics or if you're unfamiliar with high-voltage systems.