What is Hitachi ZW310-5A Fault Code 111705-6?

Fault Code 111705-6 on the Hitachi ZW310-5A wheel loader indicates a malfunction in the Engine Oil Pressure Sensor Circuit, specifically detecting an abnormal voltage signal or intermittent connection. This code is triggered when the Engine Control Module (ECM) receives voltage readings outside the expected range from the oil pressure sensor, typically below 0.5V or above 4.5V on the sensor's signal wire.

This fault is critical because the ECM relies on accurate oil pressure data to protect the Isuzu engine from catastrophic damage. The ZW310-5A's computer uses this sensor to monitor lubrication system health and will activate protective derate modes if it suspects low oil pressure conditions. For used excavators, this code often appears due to deteriorated wiring rather than actual oil pressure problems, making proper diagnosis essential before expensive component replacement.

Common Symptoms

• Engine derate mode activating, limiting RPM to approximately 1200-1500 to prevent damage
• Illuminated engine warning light or malfunction indicator on the instrument cluster
• Intermittent or constant oil pressure warning alarm sounding in the cab
• Erratic oil pressure gauge readings fluctuating between normal and zero despite stable engine operation
• Possible automatic engine shutdown in severe cases when combined with other fault codes

Potential Causes

The most common causes for Code 111705-6 on used ZW310-5A loaders include:

• Corroded or loose connector pins at the oil pressure sensor (located on the engine block near the oil filter housing)
• Wiring harness chafing against the engine block or frame rails—a known wear point on Hitachi wheel loaders with high operating hours
• Failed oil pressure sensor due to heat cycling and vibration exposure over years of operation
• ECM internal fault or poor ground connections at the ECM mounting bracket
• Contaminated engine oil causing sensor membrane failure or sludge buildup at the sensor port

How to Troubleshoot and Fix Code 111705-6

Step 1: Connect diagnostic software (Hitachi Dr.EX or compatible scan tool) to retrieve active and pending codes. Record freeze frame data showing engine conditions when the fault occurred.

Step 2: Locate the oil pressure sensor on the engine's left side near the oil filter. Disconnect the sensor harness and inspect the connector for corrosion, bent pins, or oil contamination. Clean with electrical contact cleaner and apply dielectric grease.

Step 3: Using a digital multimeter, backprobe the sensor connector with the ignition on/engine off. Verify 5V reference voltage on the signal wire and proper ground continuity (less than 0.5 ohms resistance to battery negative).

Step 4: Check sensor resistance—a functioning sensor typically reads 50-150 ohms between the signal and ground pins (consult service manual for exact specs). Replace the sensor if readings are open circuit or shorted.

Step 5: For used machines, thoroughly inspect the engine harness from sensor to ECM, particularly where it passes near the engine mount and steering components. Look for abraded insulation, a common issue after 5,000+ operating hours.

Step 6: If wiring and sensor test good, verify actual oil pressure using a mechanical gauge (should be 30-50 PSI at idle, 60-80 PSI at high idle when warm).

Professional Disclaimer: This guide provides general troubleshooting procedures. Always consult the Hitachi service manual for your specific serial number range. If unfamiliar with diesel electrical systems, seek assistance from a certified Hitachi technician to avoid misdiagnosis or ECM damage.