Hitachi ZX870LC-5A (HCMC) Fault Code 13303-2: Complete Diagnostic Guide

What is Hitachi ZX870LC-5A Fault Code 13303-2?

Fault Code 13303-2 indicates a malfunction in the Engine Control Module (ECM) communication circuit, specifically related to CAN (Controller Area Network) bus communication errors between the engine controller and other machine systems. This code triggers when the ECM detects inconsistent or interrupted data transmission on the primary communication network.

For the ZX870LC-5A equipped with the Isuzu engine platform, this fault directly impacts the machine's ability to coordinate engine performance with hydraulic demand, emission controls, and operator interface displays. The CAN bus serves as the central nervous system for modern excavators, making this a critical diagnostic priority that can affect multiple machine functions simultaneously.

Common Symptoms

When fault code 13303-2 is active, operators typically experience:

• Intermittent or complete loss of dashboard display information, including engine RPM, coolant temperature, and hydraulic oil temperature readings
• Engine derate or limp mode activation, limiting machine power output to protect components
• Multiple fault codes appearing simultaneously due to communication breakdown across systems
• Erratic hydraulic response or delayed reaction to joystick inputs as the ECM struggles to process demand signals
• Warning lights illuminating on the instrument cluster, particularly the check engine and system malfunction indicators

Potential Causes

The most common technical failures triggering this code in used ZX870LC-5A excavators include:

• Corroded or damaged CAN bus connectors at the ECM harness junction, particularly the 38-pin main connector prone to moisture intrusion
• Harness chafing and wire breaks along the right-hand frame rail where the main engine harness routes near hydraulic lines—a known wear point on high-hour machines
• Faulty termination resistors (120-ohm) at either end of the CAN network causing signal reflection and data corruption
• ECM internal failure or corrupted software, more common in machines operating in extreme temperatures or with voltage spike history
• Aftermarket component interference, especially non-OEM monitoring systems spliced into the CAN network

How to Troubleshoot and Fix Code 13303-2

Step 1: Visual Inspection and Connector Assessment Begin by inspecting all ECM connectors for corrosion, bent pins, or moisture. On used excavators, pay special attention to the connector boots—hardened or cracked boots allow water infiltration. Clean contacts with electrical contact cleaner and apply dielectric grease.

Step 2: CAN Bus Resistance Testing Using a digital multimeter, disconnect both ECM connectors and measure resistance between CAN High and CAN Low terminals (typically pins 22 and 23 on the main connector). You should read approximately 60 ohms with termination resistors intact. Readings significantly higher indicate an open circuit; lower readings suggest a short.

Step 3: Harness Continuity and Isolation Check Trace the CAN bus wiring along known friction points, particularly where the harness crosses the engine mounting bracket. Check for wire insulation wear, especially on used machines with 8,000+ hours. Perform continuity tests on both CAN High and CAN Low wires separately, then check for shorts to ground or between wires.

Step 4: Diagnostic Software Verification Connect Hitachi Dr.EX diagnostic software or compatible J1939 scan tool to monitor real-time CAN bus traffic. Observe message error rates and confirm all nodes are communicating. For used excavators with component replacements, verify all modules have compatible software versions—mismatched firmware can cause intermittent communication failures.

Step 5: Termination Resistor Verification Locate and test both 120-ohm termination resistors at the network endpoints. Failed resistors are common in older machines and cause complete communication breakdown.

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Disclaimer: This guide provides general diagnostic procedures for fault code 13303-2. Always consult the official Hitachi service manual for your specific machine serial number range. Complex electrical diagnostics may require professional technician assistance with calibrated diagnostic equipment. Improper repairs to the CAN bus system can cause additional damage to electronic control modules.