What is Hyundai HX220 NL EPFC Fault Code 1679 (3031-2)?

Fault Code 1679 (3031-2) indicates a malfunction in the Boom Swing Solenoid Valve Circuit, specifically detecting an open circuit or short to ground in the electrical pathway. This code is generated by the Electronic Control Module (ECM) when it cannot properly energize or control the boom swing function's proportional solenoid valve, which regulates hydraulic flow for combined boom and swing operations.

This fault is critical for the HX220 NL EPFC because it directly affects the excavator's ability to perform simultaneous boom and swing movements efficiently. When this circuit fails, the hydraulic system cannot receive proper electronic signals, resulting in degraded operational productivity and potential safety concerns during combined function operations.

Common Symptoms

• Intermittent or complete loss of boom swing combination function while individual boom and swing operations may still work independently
• Warning indicator illumination on the instrument cluster, often accompanied by an audible alarm
• Reduced hydraulic response or jerky movement when attempting to operate boom and swing controls simultaneously
• Error message display on the monitor panel specifically referencing hydraulic system faults
• Machine may enter derate mode limiting other hydraulic functions as a protective measure

Potential Causes

The most common technical causes for Code 1679 in used HX220 NL excavators include:

• Damaged wiring harness between the ECM and boom swing solenoid valve, particularly at known rub points near the boom base and swing bearing area
• Corroded or loose connector pins at the solenoid valve connector or ECM harness connection points (common in machines with 3,000+ operating hours)
• Failed boom swing proportional solenoid valve due to internal coil breakdown or contamination from degraded hydraulic fluid
• Moisture intrusion into the electrical connector causing intermittent short circuits or high resistance
• ECM internal driver circuit failure (less common but possible in older machines)
• Chafed insulation on wire bundle where harness passes through cab floor or swing post

How to Troubleshoot and Fix Code 1679 (3031-2)

Step 1: Visual Inspection Begin with a thorough visual examination of the wiring harness from the ECM to the boom swing solenoid valve. On used excavators, focus on areas where the harness routes near moving components or metal edges. Look for abraded insulation, pinched wires, or oil-soaked sections that indicate seal leaks affecting electrical integrity.

Step 2: Connector and Resistance Testing Disconnect the solenoid valve connector and inspect for corrosion, bent pins, or moisture. Using a digital multimeter, measure the resistance of the solenoid coil (typically 8-15 ohms for this application). Then check for continuity and shorts to ground on the harness side with all power disconnected.

Step 3: Voltage Supply Verification Reconnect the system and use a multimeter or oscilloscope to verify the ECM is providing proper PWM (Pulse Width Modulation) voltage signals to the solenoid (typically 12-24V depending on command). If voltage is present but the solenoid doesn't respond, replace the valve assembly.

Step 4: Harness Repair or Replacement For used machines, if you discover wire damage or connector corrosion, repair using proper gauge wire and heat-shrink connections, or replace the affected harness section. Always apply dielectric grease to connectors to prevent future moisture issues.

Step 5: ECM Diagnostics If all external components test correctly, connect Hyundai Hi-MATE diagnostic software to verify ECM output driver functionality and check for internal controller faults.

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Disclaimer: This guide provides general troubleshooting information. Always consult the official Hyundai service manual for your specific machine serial number and consider professional diagnostic assistance for complex electrical issues.