What is Hitachi ZX350LCK-5G Fault Code 13303-2?

Fault Code 13303-2 indicates a hydraulic pump solenoid control circuit malfunction in the main pump pressure control system. This code specifically signals that the Engine Control Module (ECM) has detected an abnormal voltage or current condition in the solenoid valve circuit responsible for regulating main hydraulic pump displacement on your Hitachi ZX350LCK-5G excavator.

This fault directly affects the machine's pump flow management system, which controls how much hydraulic fluid is delivered under various load conditions. The solenoid valve receives pulse-width modulated (PWM) signals from the ECM to adjust pump angle and maintain optimal pressure. When this circuit fails, the excavator loses its ability to efficiently match hydraulic power to operational demands, resulting in performance degradation and potential damage to the hydraulic system.

Common Symptoms

• Reduced hydraulic power across all functions, with noticeably slower boom, arm, and bucket movements
• Erratic hydraulic response where attachments move inconsistently or surge unexpectedly during operation
• Engine lugging or stalling under normal load conditions due to improper pump angle adjustment
• Warning light activation on the instrument cluster, often accompanied by audible alarm
• Machine entering derate mode, limiting engine RPM to prevent damage to hydraulic components

Potential Causes

The most common technical causes for Code 13303-2 on used ZX350LCK-5G excavators include:

• Solenoid valve coil failure due to overheating, moisture intrusion, or age-related insulation breakdown (typical resistance should be 3-5 ohms)
• Harness chafing at the pump mounting area where wiring rubs against the pump housing or frame during normal vibration
• Corroded connector pins at the solenoid connector (C-207), especially on machines operated in coastal or high-humidity environments
• ECM driver circuit failure within the controller itself, preventing proper PWM signal generation
• Intermittent short to ground caused by damaged wire insulation along the harness run from ECM to pump assembly
• Contaminated hydraulic oil causing solenoid valve spool sticking, increasing electrical load beyond normal parameters

How to Troubleshoot and Fix Code 13303-2

Step 1: Visual Inspection and Connector Check Begin by accessing the main hydraulic pump on the right side of the engine. Disconnect the solenoid valve connector (typically a 2-pin Deutsch connector) and inspect for corrosion, bent pins, or moisture. On used excavators, this connector frequently suffers from hydraulic oil mist contamination. Clean with electrical contact cleaner and check for proper pin tension.

Step 2: Solenoid Resistance Testing Using a digital multimeter, measure resistance across the solenoid coil terminals. Specifications call for 3-5 ohms at 20°C. Readings below 2 ohms indicate a short circuit; readings above 10 ohms or infinite resistance signal an open coil requiring solenoid replacement. Also perform an insulation test between each terminal and the solenoid body—you should read infinite resistance (no ground fault).

Step 3: Harness and Voltage Supply Verification With the connector still disconnected, use your multimeter to check for battery voltage (24V) at the harness supply wire with ignition on. Verify the ground circuit continuity to the ECM (should be less than 1 ohm). Inspect the entire harness from pump to ECM for rubbing points—the section passing near the hydraulic tank is particularly vulnerable on this model.

Step 4: ECM Signal Testing If solenoid and wiring test good, connect a Hitachi Dr.EX diagnostic software tool or compatible scan tool. Monitor the PWM duty cycle command to the solenoid during operation. Normal values range from 10-90% depending on load. If the ECM shows command output but no corresponding solenoid action, replace the solenoid valve assembly. If no command signal appears, suspect ECM internal driver failure.

Step 5: Used Equipment Specific Checks For older machines, remove the solenoid valve entirely and test for mechanical sticking. Disassemble and clean if hydraulic varnish is present. Check mounting bolts for proper torque (25 Nm) as vibration loosening can cause intermittent electrical connection. Replace any heat-damaged wiring sections—high underhood temperatures on used machines often cause insulation brittleness.

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Disclaimer: This guide provides general diagnostic procedures for informational purposes. Hydraulic system repairs involve high-pressure components and electrical systems. Always consult the official Hitachi service manual for your specific serial number range and consider professional diagnostic assistance for complex electrical issues or if you lack proper diagnostic equipment.