What is Hyundai HX220 NL EPFC Fault Code 4159 (5743-12)?

Fault Code 4159 (5743-12) indicates a CAN Communication Error between the Engine Control Module (ECM) and the Pump Control Module (PCM) on the Hyundai HX220 NL EPFC excavator. This code specifically signals that the data link between these two critical control units has been interrupted or degraded, preventing proper coordination between engine output and hydraulic pump delivery.

This communication failure is particularly critical on the HX220 NL EPFC because this model uses an advanced Electronic Pump Flow Control (EPFC) system that requires constant real-time data exchange between the engine and hydraulic systems. When this CAN bus communication fails, the excavator cannot optimize fuel efficiency or match hydraulic flow to engine speed, resulting in poor performance and potential component damage.

Common Symptoms

• Yellow or red warning light on the instrument cluster, often accompanied by reduced machine responsiveness
• Hydraulic system derate mode where boom, arm, and swing functions operate at significantly reduced speed
• Engine RPM fluctuations or failure to maintain consistent idle speed under load
• Intermittent loss of throttle control or delayed response when operating joysticks
• Complete shutdown of hydraulic functions while the engine continues running normally

Potential Causes

The most common technical causes for Code 4159 (5743-12) on used HX220 excavators include:

• Damaged or corroded CAN bus wiring harness between the ECM and PCM, particularly at known rub points near the engine mount and main pump area
• Loose or oxidized electrical connectors at either the ECM (located behind the operator cab) or PCM (mounted near the hydraulic pump)
• Failed terminating resistor on the CAN network causing signal reflection and data corruption
• ECM or PCM internal failure due to moisture intrusion or component aging in high-hour machines
• Low voltage supply to either control module caused by weak batteries, poor ground connections, or failing alternator

How to Troubleshoot and Fix Code 4159 (5743-12)

Step 1: Visual Inspection of CAN Bus Harness Begin by thoroughly inspecting the CAN High and CAN Low wiring between the ECM and PCM. On used excavators, focus on areas where the harness passes near moving components or sharp edges. Look for abraded insulation, pinched wires, or evidence of previous repairs. Check all connectors for corrosion, bent pins, or moisture intrusion.

Step 2: Test Electrical Connections and Voltage Using a digital multimeter, verify battery voltage at both the ECM and PCM (should read 24-28V with engine running). Check for proper grounding by measuring resistance between module cases and machine frame (should be less than 1 ohm). Disconnect and reconnect all CAN bus connectors while applying dielectric grease to prevent future corrosion.

Step 3: CAN Bus Resistance and Diagnostic Testing With all modules disconnected, measure resistance across the CAN High and CAN Low terminals—you should read approximately 60 ohms if terminating resistors are functioning correctly. Reconnect modules one at a time to isolate any short circuits. Use Hyundai Hi-MATE diagnostic software or compatible scan tool to monitor real-time CAN bus traffic and identify which module is failing to communicate.

Step 4: Replace Faulty Components If harness and connections test good, the issue likely resides in either the ECM or PCM. On high-hour used machines, PCM failures are more common due to their proximity to heat and vibration from the hydraulic pump. Replace the failed module with OEM or verified remanufactured units, ensuring proper software calibration after installation.

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Disclaimer: This guide provides general troubleshooting information for Hyundai HX220 NL EPFC excavators. Always consult the manufacturer's service manual and consider professional diagnostic assistance for complex electrical issues. Improper repairs to CAN bus systems can cause additional control module damage.