What is Hyundai HX220 NL EPFC Fault Code 4585 (4792-14)?

Fault Code 4585 (4792-14) indicates a "Fuel Injection System - Cylinder 4 Injector Circuit High Voltage" error on the Hyundai HX220 NL EPFC excavator. This code is triggered when the Electronic Control Module (ECM) detects an abnormally high voltage reading in the electrical circuit controlling the fuel injector on cylinder number 4.

This diagnostic trouble code (DTC) specifically monitors the injector driver circuit within the common rail fuel injection system. The ECM continuously measures the voltage and current flow to each injector solenoid. When cylinder 4's circuit voltage exceeds the manufacturer's predetermined threshold (typically during injector activation), the system logs this fault. This is critical for the HX220's diesel engine performance because improper injector control leads to incomplete combustion, excessive emissions, power loss, and potential engine damage. Left unaddressed, this electrical fault can cause cylinder misfires and accelerated wear on the fuel system components.

Common Symptoms

• Engine warning light or malfunction indicator lamp (MIL) illuminated on the instrument cluster
• Rough idle or engine misfiring, particularly noticeable under load or during cold starts
• Reduced engine power and throttle response, especially during heavy digging or lifting operations
• Increased fuel consumption and black or white smoke from the exhaust stack
• Engine derate mode activation in severe cases, limiting maximum RPM to protect the engine

Potential Causes

The most common technical causes for Code 4585 on used Hyundai excavators include:

• Damaged or chafed injector wiring harness - particularly at flex points near the valve cover or where the harness routes along the engine block (a known wear area on high-hour HX220 machines)
• Failed fuel injector solenoid on cylinder 4, causing internal short circuits or open windings
• Corroded or loose electrical connectors at the injector plug or ECM connection points due to moisture intrusion
• ECM driver circuit failure - internal ECM component degradation affecting the cylinder 4 output channel
• Incorrect injector replacement - aftermarket or wrong-specification injectors with improper resistance values
• Damaged injector return circuit causing voltage feedback issues in older machines with 8,000+ operating hours

How to Troubleshoot and Fix Code 4585 (4792-14)

Step 1: Visual Inspection and Connector Check Begin by performing a thorough visual inspection of the cylinder 4 injector wiring harness. On used excavators, check for rubbing points where the harness contacts the engine block, valve cover edges, or hydraulic lines. Disconnect the injector connector and inspect for corrosion, bent pins, or moisture. Clean contacts with electrical contact cleaner and apply dielectric grease before reconnecting.

Step 2: Resistance and Voltage Testing Using a digital multimeter, measure the injector solenoid resistance at cylinder 4. The specification for HX220 injectors typically ranges between 0.3-0.8 ohms (consult your service manual for exact values). With the ignition on and engine off, check for supply voltage at the injector connector—you should see battery voltage (approximately 24V on this model). Also measure resistance between the injector terminals and ground; infinite resistance indicates proper insulation.

Step 3: Injector Swap Test If resistance values are within specification but the code persists, swap the cylinder 4 injector with another cylinder (such as cylinder 2). Clear the fault codes using diagnostic software (Hyundai Hi-MATE or compatible scan tool), and run the engine. If the fault code moves to the new cylinder location, the injector itself is faulty and requires replacement. If the code remains on cylinder 4, the problem lies in the wiring harness or ECM driver circuit.

Step 4: Harness Continuity and ECM Testing Check continuity from the injector connector through to the ECM connector pins. Refer to the wiring diagram for specific pin locations. Look for resistance above 5 ohms, which indicates damaged wiring. For used excavators with high hours, pay special attention to harness sections that pass through grommets or near heat sources. If wiring tests good but the fault persists, the ECM driver circuit for cylinder 4 may be damaged—this requires ECM replacement or professional repair.

Step 5: Final Verification After repairs, clear all fault codes and perform a dynamic injector test using diagnostic software to verify proper injector operation across all cylinders. Monitor live data during engine operation to confirm voltage levels remain within normal parameters (typically 40-120V during injection events on common rail systems).

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Disclaimer: This guide provides general troubleshooting information for experienced diesel mechanics. Always consult the official Hyundai service manual for your specific machine serial number and software version. If you're uncomfortable performing electrical diagnostics or lack proper diagnostic equipment, consult a certified Hyundai heavy equipment technician to avoid costly misdiagnosis or further damage to the fuel injection system.