What is Hitachi ZX210LCN-5B Fault Code 19903-3?

Fault Code 19903-3 on the Hitachi ZX210LCN-5B excavator indicates a communication error between the Engine Control Module (ECM) and the Hydraulic Control Module (HCM), specifically a CAN bus communication timeout or data transmission failure. This code is triggered when the ECM fails to receive expected signals from the HCM within a predetermined time frame, disrupting the integrated control system that manages engine performance relative to hydraulic demand.

This fault is critical for the ZX210LCN-5B because this model relies heavily on coordinated communication between control modules to optimize fuel efficiency and hydraulic performance. When communication fails, the machine's automatic power mode and load-sensing hydraulic system cannot function properly, potentially reducing productivity and increasing fuel consumption.

Common Symptoms

• Warning light illuminated on the instrument panel, often accompanied by a message indicating communication fault
• Reduced engine power or inability to access high-power work modes, limiting digging force and cycle times
• Erratic hydraulic response, including inconsistent swing speed or boom/arm movements during combined operations
• Engine may not respond correctly to hydraulic load demands, causing the engine to bog down or over-rev unexpectedly
• Intermittent loss of monitoring data on the display panel, such as fuel consumption or hydraulic oil temperature readings

Potential Causes

• Damaged or corroded CAN bus wiring harness between the ECM and HCM—particularly at flex points near the engine mounting or cab pivot where harnesses experience repeated movement
• Loose or corroded connector pins at either the ECM or HCM connection points, common in used machines exposed to moisture and vibration
• Failed termination resistor on the CAN bus network, causing signal reflection and data corruption
• Voltage supply issues to either control module, often from corroded ground connections or failing relays in older machines
• ECM or HCM internal failure, though less common than wiring/connector issues in used equipment
• Aftermarket modifications or improper repairs that compromised the CAN bus network integrity

How to Troubleshoot and Fix Code 19903-3

Step 1: Visual Inspection of Wiring and Connectors Begin by inspecting the CAN bus harness running between the ECM (located near the battery box) and the HCM (typically mounted near the hydraulic pump). Check for obvious damage, chafing against metal edges, or oil contamination. On used excavators, pay special attention to harness routing near the engine mounts where vibration causes wear. Disconnect and inspect all relevant connectors for bent pins, corrosion (green/white deposits), or moisture intrusion.

Step 2: Test CAN Bus Continuity and Resistance Using a digital multimeter, measure the resistance between the CAN-High and CAN-Low wires at the disconnected ECM connector. You should read approximately 60 ohms if termination resistors are functioning correctly (typically 120 ohms at each end = 60 ohms total). Check continuity of each individual CAN wire from ECM to HCM—any open circuit indicates a broken wire requiring repair or harness replacement.

Step 3: Verify Power Supply and Ground Circuits Check that both the ECM and HCM are receiving proper supply voltage (typically 24V on this model). Verify ground connections are clean and tight—remove ground terminals, clean contact surfaces with a wire brush, and apply dielectric grease before reconnecting. Corroded grounds are extremely common in used machines and cause numerous communication faults.

Step 4: Utilize Hitachi Diagnostic Software Connect Hitachi Dr.EX diagnostic software via the machine's diagnostic port to monitor real-time CAN bus activity and pinpoint whether the ECM or HCM is failing to transmit/receive. The software can identify specific message failures and help isolate which module is at fault. Check for additional stored codes that may indicate the root cause.

Step 5: Component Replacement (If Necessary) If wiring, connectors, and power supplies test normal, the fault likely resides in either the ECM or HCM. Before replacing expensive control modules on a used excavator, consider sourcing tested used modules or having your existing module professionally tested and repaired, as complete replacement can be cost-prohibitive.

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Disclaimer: This guide provides general troubleshooting information for educational purposes. Always consult the official Hitachi service manual for your specific machine serial number and seek assistance from qualified Hitachi technicians for complex electrical diagnostics. Improper repairs can cause additional damage or safety hazards.