Hitachi ZX350K-5G Fault Code 13304-2: Complete Diagnostic Guide

What is Hitachi ZX350K-5G Fault Code 13304-2?

Fault Code 13304-2 indicates a malfunction in the hydraulic pump flow control solenoid circuit, specifically detecting an abnormal voltage condition or open circuit in the pump control system. This code is triggered when the Electronic Control Module (ECM) detects that the electrical signal to the hydraulic pump's proportional flow control solenoid falls outside acceptable parameters.

In the ZX350K-5G model, this solenoid regulates hydraulic pump output based on operational demand. The system constantly monitors voltage feedback to ensure precise flow control. When voltage deviates from the 8-28V operating range or shows complete circuit interruption, the ECM logs this fault to prevent potential hydraulic system damage or inefficient operation. This is critical because improper pump flow control directly affects machine productivity, fuel efficiency, and can lead to overheating in the hydraulic system.

Common Symptoms

Operators typically experience the following when Code 13304-2 is active:

• Reduced hydraulic power across all functions (boom, arm, bucket, swing)
• Engine derate mode activation, limiting RPM to protect the system
• Amber warning light illuminated on the instrument cluster
• Sluggish or inconsistent machine response during combined hydraulic operations
• Increased fuel consumption due to pump running at default settings rather than demand-based control

Potential Causes

The most common technical causes for this fault code on used ZX350K-5G excavators include:

• Damaged wiring harness near the hydraulic pump mounting area where vibration and heat cause insulation breakdown
• Corroded connector pins at the solenoid plug (common in machines operating in wet or coastal environments)
• Failed proportional solenoid coil due to age-related internal short or open circuit
• Chafed wires at known rub points near the main pump where harness routing contacts metal edges
• ECM internal fault (less common) affecting the solenoid driver circuit
• Loose or oxidized ground connections at the pump assembly mounting bolts

How to Troubleshoot and Fix Code 13304-2

Step 1: Visual Inspection Begin by inspecting the wiring harness from the ECM to the hydraulic pump solenoid. On used excavators, pay particular attention to areas where the harness passes near hot surfaces or sharp edges. Check the solenoid connector for corrosion, bent pins, or moisture intrusion. Clean connections with electrical contact cleaner and verify the connector locks securely.

Step 2: Electrical Testing Using a digital multimeter (DMM), disconnect the solenoid connector and measure coil resistance across the solenoid terminals. Normal resistance should read between 3-7 ohms (consult your service manual for exact specifications). Next, check for continuity in the harness from the ECM connector to the solenoid plug—any reading above 1 ohm indicates damaged wiring requiring repair or replacement.

Step 3: Voltage Supply Check With the ignition on and engine off, backprobe the solenoid connector to verify supply voltage from the ECM. You should measure approximately 12V on the power supply wire. If voltage is absent, trace back to the ECM and check related fuses and relay circuits. For used machines, inspect all ground connections at the pump mounting—remove, clean with a wire brush, and apply dielectric grease before reinstalling.

Step 4: Solenoid Replacement or Harness Repair If resistance or voltage tests fail, replace the proportional flow control solenoid (Hitachi Part Number varies by production year—verify with your dealer). When installing on used equipment, always replace the connector seal and apply fresh dielectric grease. If harness damage is found, repair with OEM-grade wire and heat-shrink connections, ensuring proper routing away from heat and friction points.

Step 5: Clear Code and Verify After repairs, use Hitachi diagnostic software (Dr.EX) or a compatible scan tool to clear the fault code. Run the machine through all hydraulic functions under load and monitor for code recurrence. Check that the system exits derate mode and normal hydraulic response returns.

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Disclaimer: This guide provides general troubleshooting information for Code 13304-2. Hydraulic and electrical system repairs should be performed by qualified technicians with appropriate training and tools. Always consult the official Hitachi ZX350K-5G service manual and follow proper lockout/tagout procedures before performing diagnostics or repairs.