What is Hitachi ZW310-5A Fault Code 111704-9?

Fault Code 111704-9 on the Hitachi ZW310-5A wheel loader indicates a malfunction in the Engine Oil Pressure Sensor Circuit, specifically a signal voltage that is abnormally low or experiencing an intermittent open circuit condition. This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) detects that the voltage signal from the engine oil pressure sensor has fallen below the manufacturer's specified threshold (typically below 0.5 volts) or has completely dropped out.

This code is critical for the ZW310-5A because the engine oil pressure monitoring system is a primary safeguard against catastrophic engine damage. The Isuzu 6WG1X diesel engine powering this loader relies on precise oil pressure data to prevent operation under dangerous low-pressure conditions that could lead to bearing failure, connecting rod damage, or complete engine seizure. When this fault is active, the ECM may trigger protective derate modes or emergency shutdown sequences to preserve engine integrity.

Common Symptoms

• Engine oil pressure warning lamp illuminated continuously on the instrument cluster (red oil can symbol)
• Engine power derate or reduced maximum RPM, limiting machine performance during heavy loading operations
• Intermittent engine shutdown during warm-up or under load, especially on used machines with worn sensors
• Audible warning alarm sounding in the cab, alerting the operator to abnormal oil pressure conditions
• ECM data logging shows erratic or flatlined oil pressure readings when accessed through diagnostic software

Potential Causes

In used Hitachi ZW310-5A loaders, this fault code commonly stems from age-related failures specific to high-hour machines:

• Failed engine oil pressure sensor due to internal diaphragm degradation or contaminated sensing element (common after 8,000+ operating hours)
• Damaged wiring harness at known rub points near the engine mount bracket or where the harness passes over the valve cover
• Corroded or loose electrical connectors at the sensor termination point, especially on machines operated in coastal or high-moisture environments
• ECM internal circuit failure or damaged input channel (less common but documented on 2013-2015 model years)
• Low actual engine oil pressure caused by worn oil pump, clogged oil filter, or using incorrect viscosity oil in cold conditions
• Frayed ground wire connections creating intermittent voltage fluctuations in the sensor circuit

How to Troubleshoot and Fix Code 111704-9

Step 1: Visual Inspection and Preliminary Checks Begin by performing a thorough harness inspection from the oil pressure sensor (located on the left side of the engine block near the oil filter housing) to the ECM connector. On used excavators, check for harness abrasion where the wire bundle contacts the engine valve cover and air compressor mounting bracket—these are known wear points on the ZW310-5A. Inspect the sensor connector for oil contamination, corrosion, or bent pins. Clean connectors with electrical contact cleaner and ensure positive engagement.

Step 2: Sensor Circuit Voltage Testing Using a digital multimeter (DMM), backprobe the oil pressure sensor connector with the ignition ON/engine OFF. Measure the reference voltage from the ECM; you should see approximately 5.0 volts DC on the signal wire. If voltage is absent or significantly low, trace the circuit back toward the ECM, checking for open circuits or short-to-ground conditions. Test the sensor ground circuit for continuity to chassis ground (should read less than 1 ohm resistance).

Step 3: Sensor Resistance and Functional Testing Disconnect the oil pressure sensor and measure its internal resistance across the terminals. A functioning sensor typically shows 50-250 ohms at room temperature (consult Hitachi service manual for exact specifications). Install a mechanical oil pressure gauge at the sensor port and start the engine—verify actual oil pressure reaches 45-60 PSI at operating temperature and idle (minimum 15 PSI). If mechanical pressure is normal but the sensor reads incorrectly, replace the sensor with a genuine Hitachi part (P/N 4621723 or equivalent).

Step 4: Advanced Diagnostics for Persistent Codes If the fault persists after sensor replacement, connect Hitachi Dr.EX diagnostic software or equivalent J1939 scan tool to monitor live oil pressure sensor data. Compare ECM readings to mechanical gauge values. Check for ECM software updates addressing sensor circuit sensitivity issues (TSB updates were released for 2014-2016 models). Inspect ECM connector pins for corrosion or terminal push-back. For used machines with high hours, consider testing the ECM 5-volt reference circuit under load, as voltage drop below 4.85V can trigger false codes.

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Professional Disclaimer: This guide provides general troubleshooting information for experienced diesel mechanics. Always consult the official Hitachi ZW310-5A service manual for torque specifications, exact sensor values, and safety procedures. Improper diagnosis may lead to engine damage. If uncertain, contact a certified Hitachi dealer or qualified heavy equipment technician.