What is Hitachi ZW310-5A Fault Code 111702-9?

Fault Code 111702-9 on the Hitachi ZW310-5A indicates a hydraulic pump solenoid valve circuit malfunction, specifically related to the main pump flow control system. This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) detects an abnormal electrical signal from the proportional solenoid valve that regulates hydraulic pump displacement and system pressure.

This code is critical for the ZW310-5A because the hydraulic pump control solenoid directly affects the machine's ability to modulate power delivery across all hydraulic functions. When this circuit fails, the excavator's load-sensing hydraulic system cannot properly adjust pump output, leading to reduced productivity, excessive fuel consumption, and potential damage to the hydraulic pump itself. On used excavators, this fault commonly develops due to electrical connector corrosion or solenoid coil degradation from years of exposure to heat and vibration.

Common Symptoms

• Reduced hydraulic power across all functions (boom, arm, bucket, swing) with sluggish movement response
• Intermittent or continuous warning light on the instrument panel indicating a hydraulic system fault
• Erratic engine RPM fluctuations as the ECM attempts to compensate for improper pump signal feedback
• Excessive engine speed without corresponding hydraulic performance (pump not loading properly)
• Stored fault code in ECM memory even after machine restart, preventing code from self-clearing

Potential Causes

The most common technical causes for Code 111702-9 on used ZW310-5A excavators include:

• Damaged or corroded wiring harness at the pump solenoid connector, especially where the harness passes near the hydraulic tank (known rub point on this model)
• Failed proportional solenoid valve coil within the main hydraulic pump assembly due to thermal degradation or internal short circuit
• Broken or frayed wires in the engine-to-pump harness bundle from prolonged vibration exposure
• ECM power supply issues causing insufficient voltage delivery to the solenoid valve circuit
• Contaminated electrical connectors with hydraulic oil or moisture infiltration creating resistance faults
• Faulty ECM output driver for the solenoid control circuit (less common but possible on high-hour machines)

How to Troubleshoot and Fix Code 111702-9

Step 1: Visual Inspection and Connector Check Begin by accessing the main hydraulic pump located on the right side of the engine. Disconnect the solenoid valve electrical connector and carefully inspect both the male and female terminals for corrosion, bent pins, or hydraulic fluid contamination. On used excavators, this connector frequently shows green corrosion due to moisture ingress. Clean connectors with electrical contact cleaner and apply dielectric grease before reconnection.

Step 2: Electrical Circuit Testing Using a digital multimeter (DMM), check the solenoid coil resistance. With the connector disconnected, measure across the solenoid terminals—the typical specification is 8-15 ohms at room temperature. Values outside this range indicate a failed solenoid coil requiring replacement. Next, check for harness continuity from the ECM connector to the pump solenoid connector, ensuring no open circuits or shorts to ground exist.

Step 3: Power Supply and Signal Verification With the ignition on (engine off), use your multimeter to verify the ECM is supplying 12-14 volts to the solenoid circuit when commanded. If using Hitachi Dr.EX diagnostic software, monitor the solenoid command signal percentage while operating the machine. A discrepancy between commanded and actual signal indicates either wiring resistance or ECM output failure.

Step 4: Harness Inspection for Known Wear Points On the ZW310-5A, carefully trace the harness from the pump forward to the ECM, paying special attention to where it contacts the hydraulic tank mounting bracket and crosses near the engine oil cooler. These are common friction points where insulation wears through on used machines with over 5,000 hours. Repair any damaged sections with heat-shrink tubing and secure with proper loom clamps.

Step 5: Component Replacement and Code Clearing If diagnostics confirm solenoid failure, replace the proportional control solenoid valve (Hitachi part number varies by pump manufacturer—check your specific pump model). After repairs, clear the fault code using diagnostic software and perform a complete hydraulic function test under load to verify proper pump response and ensure the code does not return.

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Disclaimer: This guide provides general troubleshooting information for Code 111702-9. Always consult the official Hitachi ZW310-5A service manual for model-specific procedures and specifications. For complex hydraulic or electrical issues, especially on used equipment with unknown maintenance history, seek diagnosis from a certified Hitachi technician or qualified heavy equipment mechanic to prevent costly misdiagnosis or further machine damage.