What is Hyundai HX220 NL EPFC Fault Code 141 (100-4)?

Fault Code 141 (100-4) on the Hyundai HX220 NL EPFC indicates an Engine Coolant Temperature (ECT) Sensor Circuit Low Voltage condition. This diagnostic trouble code triggers when the Engine Control Module (ECM) detects an abnormally low voltage signal from the coolant temperature sensor, typically below 0.2 volts, indicating a potential short to ground or sensor failure.

The ECT sensor is critical for the HX220's engine management system because it directly influences fuel injection timing, idle speed control, and engine warm-up strategies. When this sensor provides inaccurate data, the ECM cannot properly regulate engine temperature, potentially leading to poor fuel economy, increased emissions, and inadequate engine protection against overheating or overcooling conditions.

Common Symptoms

• Check Engine Light or malfunction indicator lamp illuminated on the dashboard
• Engine running excessively rich, producing black smoke from the exhaust
• Hard starting or extended cranking time, especially in cold conditions
• Engine fails to reach normal operating temperature or runs cooler than expected
• Rough idle or poor throttle response during initial warm-up periods
• Cooling fan may run continuously at high speed regardless of actual engine temperature

Potential Causes

The most common technical reasons for Code 141 (100-4) on used HX220 excavators include:

• ECT sensor internal failure or contamination causing incorrect resistance readings
• Damaged or chafed sensor wiring harness, particularly near the engine block where vibration and heat cycling cause insulation breakdown
• Corroded or loose electrical connectors at the sensor or ECM terminals
• Short to ground in the signal wire between the sensor and ECM
• Failed ECM (rare, but possible in high-hour machines with moisture intrusion)
• Incorrect sensor installation or use of non-OEM replacement parts with incompatible resistance curves

How to Troubleshoot and Fix Code 141 (100-4)

Step 1: Visual Inspection Begin by locating the ECT sensor on the engine block (typically near the thermostat housing). Inspect the wiring harness for obvious damage, rubbing against brackets, or heat damage. Check the connector for corrosion, bent pins, or moisture intrusion—common issues on used excavators operating in harsh environments.

Step 2: Sensor Resistance Testing Disconnect the ECT sensor connector and use a digital multimeter to measure resistance across the sensor terminals. At 68°F (20°C), resistance should typically read 2,000-3,000 ohms; at 176°F (80°C), approximately 300-400 ohms. Compare readings against Hyundai specifications. If readings are out of range or show infinite resistance, replace the sensor.

Step 3: Circuit Voltage Testing With the sensor disconnected and ignition on, measure voltage at the ECM side of the harness connector. You should see approximately 5 volts reference voltage from the ECM. If voltage is absent, check for open circuits or damaged wiring. Measure resistance to ground on the signal wire—it should show infinite resistance. Low resistance indicates a short to ground requiring harness repair.

Step 4: Verify Repair and Clear Code After replacing faulty components, reconnect all connections and use Hyundai diagnostic software or a compatible scan tool to clear the fault code. Run the engine through a complete warm-up cycle and monitor for code recurrence.

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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 services for complex electrical issues or if you lack proper testing equipment.