What is Hitachi ZX200LC-5G Fault Code 16607-2?

Fault Code 16607-2 on the Hitachi ZX200LC-5G indicates a DEF (Diesel Exhaust Fluid) temperature sensor circuit malfunction, specifically an implausible or out-of-range signal from the temperature sensor within the SCR (Selective Catalytic Reduction) system. This code triggers when the ECM (Engine Control Module) detects that the DEF temperature reading doesn't correlate with expected values based on engine operating conditions or ambient temperature.

This fault is critical for Tier 4 Final compliant excavators like the ZX200LC-5G because the SCR system relies on accurate DEF temperature data to optimize injection rates and maintain emissions compliance. When this sensor fails or provides incorrect readings, the system cannot properly manage NOx (nitrogen oxide) emissions, potentially leading to engine derate or shutdown to protect emissions equipment.

Common Symptoms

• Amber or red warning light on the instrument cluster indicating an emissions system fault
• Engine power derate (typically 25-40% reduction) after a predetermined grace period, usually 2-4 hours of operation
• DEF quality warning appearing on the display, even with fresh fluid
• Increased diesel consumption due to improper SCR system calibration
• Frequent DEF system-related alarms or messages on the monitor panel

Potential Causes

The most common causes for Code 16607-2 on used ZX200LC-5G excavators include:

• Failed DEF temperature sensor due to crystallized urea buildup from contaminated or old DEF fluid
• Corroded or damaged wiring harness connectors at the DEF tank, especially where the harness routes near the tank mounting bracket (known rub point on this model)
• Broken or chafed wires in the sensor circuit, particularly in the section running along the left-side frame rail
• ECM software calibration issues requiring updates (common on early 2014-2015 production units)
• Poor electrical ground connection at the DEF tank assembly or chassis ground points
• Water intrusion into the sensor connector from damaged seals or improper tank service procedures

How to Troubleshoot and Fix Code 16607-2

Step 1: Initial Inspection and Data Collection Connect Hitachi Dr.EX diagnostic software or a compatible J1939 scan tool to retrieve active and pending codes. Record freeze frame data, particularly DEF temperature readings versus engine coolant temperature. Visually inspect the DEF tank sensor connector (located on top of the tank assembly) for corrosion, bent pins, or moisture. On used excavators, this connector frequently shows green corrosion due to DEF vapor exposure.

Step 2: Electrical Circuit Testing Disconnect the DEF temperature sensor connector and measure resistance across the sensor terminals using a digital multimeter. At 68°F (20°C), resistance should read approximately 2,200-2,500 ohms (consult service manual for exact specifications). Test the wiring harness for continuity from sensor connector to ECM pin locations (typically pins 37 and 38 on the engine harness connector). Check for shorts to ground or power using the multimeter's resistance function—readings should show infinite resistance (open circuit).

Step 3: Sensor Replacement and Harness Repair If resistance values are out of specification or erratic, replace the DEF temperature sensor (Hitachi part number 4676385 or equivalent). Before installation, thoroughly clean the sensor mounting area on the DEF tank to remove any crystallized urea deposits. For used machines, carefully inspect the entire sensor harness for wear points, especially where it passes through the frame bracket approximately 18 inches from the tank. Repair any chafed sections with heat-shrink tubing and apply protective loom. Apply dielectric grease to connector pins before reassembly to prevent future corrosion.

Step 4: System Verification Clear fault codes using diagnostic software and operate the machine through multiple temperature cycles (cold start to full operating temperature). Monitor live DEF temperature data—it should track within 10-15°F of engine coolant temperature during warm-up. Verify no codes return after 30 minutes of normal operation.

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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 follow proper safety procedures. If unfamiliar with electrical diagnostics or emissions systems, seek assistance from a certified Hitachi dealer or qualified heavy equipment technician.