What is Hitachi ZX870-5A Fault Code 13303-2?

Fault Code 13303-2 on the Hitachi ZX870-5A indicates a malfunction in the hydraulic pump solenoid circuit, specifically detecting an abnormal current or short circuit condition in the pump flow control system. This diagnostic trouble code (DTC) is generated when the Electronic Control Module (ECM) detects electrical irregularities in the solenoid valve that regulates hydraulic pump displacement and flow rates.

In the ZX870-5A's advanced hydraulic system, this solenoid plays a critical role in matching pump output to operational demand, directly affecting fuel efficiency and hydraulic performance. When this circuit fails, the excavator's ability to optimize power distribution across multiple hydraulic functions becomes severely compromised, potentially leading to reduced productivity and increased fuel consumption.

Common Symptoms

When Code 13303-2 is active, operators typically experience:

• Hydraulic system derate with noticeably reduced swing speed and arm/boom response times
• Illuminated warning lamp on the instrument cluster, often accompanied by an audible alarm
• Erratic pump performance including inconsistent flow rates during combined hydraulic functions
• Engine RPM fluctuations when attempting high-demand operations like heavy digging or lifting
• Increased hydraulic oil temperature due to inefficient pump control and pressure regulation

Potential Causes

The most common technical causes for this fault code in used ZX870-5A excavators include:

• Damaged solenoid wiring harness near the hydraulic pump mounting area where cables experience vibration and heat exposure
• Failed pump flow control solenoid valve due to internal coil degradation or contamination from hydraulic fluid breakdown
• Corroded electrical connectors at the solenoid connection point, particularly in machines operating in high-moisture environments
• Short circuit to ground caused by harness chafing against the pump housing or frame components
• ECM internal faults or corrupted calibration data (less common but possible in high-hour machines)
• Voltage supply issues from the main power distribution harness or failing relays

How to Troubleshoot and Fix Code 13303-2

Step 1: Visual Inspection and Connector Check Begin by accessing the hydraulic pump assembly and inspecting the solenoid valve connector for corrosion, oil contamination, or damaged pins. On used excavators, pay special attention to the wiring harness routing—look for signs of rubbing against the pump body or nearby components, a common failure point after 5,000+ operating hours.

Step 2: Electrical Testing with Multimeter Using a quality digital multimeter, disconnect the solenoid connector and measure coil resistance across the solenoid terminals. Typical resistance should read between 10-30 ohms (consult service manual for exact specification). Next, check for continuity to ground on both wiring harness sides—any reading below 10k ohms indicates insulation breakdown or short circuit conditions.

Step 3: Power Supply Verification With the ignition on (engine off), backprobe the harness connector to verify the solenoid receives proper supply voltage (typically 12-24V depending on system design). Use Hitachi Dr. EX diagnostic software to command the solenoid on/off while monitoring current draw—normal operation draws 0.5-2.0 amps depending on specification.

Step 4: Component Replacement and Harness Repair If electrical tests confirm solenoid failure, replace the pump flow control solenoid valve with genuine Hitachi parts. For used machinery, always inspect and repair harness damage using proper heat-shrink connectors and protective loom. Reroute cables away from heat sources and secure with new clamps to prevent future chafing.

Step 5: Code Clearing and Verification After repairs, clear fault codes using diagnostic software and perform a complete hydraulic system function test under load. Monitor for code reoccurrence during a 30-minute operational cycle including all hydraulic functions.

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Disclaimer: This guide provides general troubleshooting information for experienced technicians. Always consult the official Hitachi service manual for your specific machine serial number and seek professional assistance for complex electrical diagnostics or hydraulic system repairs.