What is Hyundai HX220 NL EPFC Fault Code 105-0?

Fault Code 105-0 on the Hyundai HX220 NL EPFC indicates an Intake Air Heater Circuit malfunction, specifically detecting an abnormal voltage or open circuit in the intake air heater relay system. This code is triggered when the Electronic Control Module (ECM) detects that the intake air heater is not functioning within the manufacturer's specified parameters during cold start conditions.

The intake air heater is critical for diesel engine performance, especially in cold weather operations. It preheats incoming air to improve combustion efficiency during startup, reduce white smoke, and minimize engine wear. On the HX220 NL EPFC model, this system is particularly important because the common rail fuel injection system requires proper air temperature for optimal atomization and clean combustion during initial cranking.

Common Symptoms

When Code 105-0 is active, operators typically experience:

• Hard starting or extended cranking time, especially in temperatures below 50°F (10°C)
• Excessive white or gray smoke from the exhaust during cold starts
• Rough idle for the first 2-3 minutes after startup
• Check Engine Light (CEL) illuminated on the instrument cluster
• Reduced engine performance during warm-up period with potential power derate

Potential Causes

The most common technical reasons for Code 105-0 on used HX220 excavators include:

• Faulty intake air heater relay or relay contact degradation (common failure point after 5,000+ hours)
• Open circuit or short in the air heater wiring harness, particularly where it routes near the engine block (known rub point)
• Corroded or loose electrical connectors at the air heater element or relay socket
• Failed intake air heater element due to carbon buildup or thermal fatigue
• ECM internal relay driver circuit failure (less common but documented in older units)
• Blown fuse in the intake air heater circuit (check F23 in the main fuse box)

How to Troubleshoot and Fix Code 105-0

Step 1: Visual Inspection Begin by inspecting the intake air heater wiring harness from the ECM to the heater element. On used excavators, check for wire insulation damage where the harness contacts the engine valve cover or fuel lines. Inspect all electrical connectors for corrosion, moisture intrusion, or pushed-back pins—common issues in machines operating in wet or dusty conditions.

Step 2: Test the Relay and Circuit Locate the intake air heater relay in the main relay panel (typically near the battery box). With the ignition off, remove the relay and test for continuity using a multimeter. The relay coil should measure 80-120 ohms. Next, check for battery voltage (12V) at the relay socket with the key in the ON position. If voltage is absent, trace back to the ECM connector and check pin 47 for output signal.

Step 3: Test the Heater Element Disconnect the intake air heater element (located in the intake manifold). Using a multimeter, measure resistance across the heater terminals—it should read 0.5-2.0 ohms. An infinite reading indicates an open element requiring replacement. Also check for continuity to ground, which should be infinite (no short circuit).

Step 4: Advanced Diagnostics Connect Hyundai Hi-Mate diagnostic software or an equivalent J1939-compatible scan tool to monitor live data. Command the intake air heater ON and observe actual vs. commanded status. If the ECM shows activation but no current draw is detected, the issue lies between the relay and heater element. For used machinery, pay special attention to corroded ground connections at the engine block—clean and apply dielectric grease.

Disclaimer: This guide provides general troubleshooting information for educational purposes. Always consult the official Hyundai service manual for your specific machine serial number and consult a certified heavy equipment technician for complex electrical diagnostics or repairs involving the ECM.