What is Hitachi ZX200LC-5G Fault Code 16606-4?

Fault Code 16606-4 on the Hitachi ZX200LC-5G indicates a "Injector Cylinder 4 - Current Below Normal or Open Circuit" condition. This diagnostic trouble code (DTC) is triggered when the Engine Control Module (ECM) detects abnormally low current flow or a complete circuit interruption in the fuel injector circuit for cylinder number 4.

This code specifically relates to the common rail fuel injection system, where the ECM continuously monitors electrical current to each injector solenoid. When current drops below the manufacturer's specified threshold (typically during injector actuation), the system flags this fault. For the ZX200LC-5G's Isuzu engine, proper injector operation is critical for maintaining fuel efficiency, power output, and emissions compliance. Ignoring this code can lead to rough running, increased fuel consumption, and potential damage to the catalytic converter from unburned fuel.

Common Symptoms

• Engine misfiring or noticeably rough idle, especially when cold
• Reduced engine power and sluggish throttle response under load
• Check Engine Light (CEL) or malfunction indicator lamp illuminated on the dash
• Black or white smoke from the exhaust during operation
• Increased fuel consumption and difficulty maintaining consistent RPM

Potential Causes

The most common causes for Code 16606-4 on used ZX200LC-5G excavators include:

• Faulty cylinder 4 fuel injector with an open or shorted solenoid coil (common after 6,000+ operating hours)
• Damaged wiring harness between the ECM and injector connector, particularly where the harness routes near the engine block and experiences vibration wear
• Corroded or loose electrical connectors at the injector plug—moisture intrusion is frequent on older machines
• Failed ECM injector driver circuit (less common but possible on high-hour machines)
• Poor ground connections at the engine block or ECM mounting points

How to Troubleshoot and Fix Code 16606-4

Step 1: Visual Inspection Begin by inspecting the injector wiring harness for cylinder 4. Look for abraded insulation, pinched wires near mounting brackets, or corrosion at the injector connector. On used excavators, check where harnesses contact hot engine surfaces or moving components.

Step 2: Electrical Testing Disconnect the cylinder 4 injector connector. Using a digital multimeter, measure the injector solenoid resistance (should be 0.3-0.8 ohms for most Isuzu injectors). Then check for voltage supply at the harness side with the key on (should read battery voltage). Verify ground continuity to the ECM.

Step 3: Swap Test If resistance and voltage are correct, swap the cylinder 4 injector with another cylinder's injector. Clear codes and run the engine. If the fault code moves to the new cylinder location, the injector is faulty. If the code stays at cylinder 4, suspect wiring or ECM issues.

Step 4: Advanced Diagnostics Use Hitachi Dr.EX diagnostic software or compatible scan tool to perform an injector cut-out test and monitor real-time injector current draw during operation.

Disclaimer: This guide provides general troubleshooting information. Always consult the official Hitachi service manual and consider professional diagnostic assistance for complex electrical issues.