What is Hyundai HX220 NL EPFC Fault Code 1922 (3251-0)?

Fault Code 1922 (3251-0) on the Hyundai HX220 NL EPFC indicates an abnormal voltage signal or open circuit detected in the Engine Coolant Temperature (ECT) sensor circuit. This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) receives a voltage reading outside the normal operating range—typically above 4.5 volts or below 0.5 volts—from the coolant temperature sensor.

The ECT sensor plays a critical role in the HX220's engine management system by monitoring coolant temperature and sending data to the ECM. This information directly affects fuel injection timing, idle speed control, and engine warm-up cycles. When this circuit fails, the ECM cannot accurately regulate engine performance, potentially leading to poor fuel economy, difficult starting, or engine protection mode activation.

Common Symptoms

• Check Engine Light illuminated on the instrument cluster with reduced engine power
• Engine runs rough during cold starts or fails to reach normal operating temperature
• Cooling fan runs continuously at high speed, even when engine is cold
• Engine derate mode activated, limiting maximum RPM to protect components
• Black smoke from exhaust due to improper fuel-air mixture compensation

Potential Causes

The most common technical failures triggering Code 1922 in used HX220 excavators include:

• ECT sensor internal failure due to age-related degradation or coolant contamination
• Damaged or corroded wiring harness connections at the sensor connector—particularly common where the harness routes near the engine block and experiences heat cycling
• Open circuit caused by broken wires inside the insulation, often at flex points near the sensor
• Corroded or loose ground connections affecting sensor reference voltage
• ECM internal fault (rare, but possible in high-hour machines with moisture intrusion)
• Incorrect coolant mixture causing sensor element deterioration over time

How to Troubleshoot and Fix Code 1922 (3251-0)

Step 1: Visual Inspection Begin by inspecting the ECT sensor connector located on the engine block near the thermostat housing. Check for corrosion, bent pins, moisture intrusion, or loose connections. On used excavators, examine the entire wiring harness for signs of chafing against the engine block, heat damage, or previous repair attempts.

Step 2: Electrical Testing Using a digital multimeter, disconnect the ECT sensor and measure resistance across the sensor terminals. At 68°F (20°C), resistance should read approximately 2,500-3,000 ohms (verify exact specification in service manual). Next, check for continuity in the wiring from the sensor connector back to the ECM pins—resistance should be less than 5 ohms.

Step 3: Voltage Signal Test With the ignition on and sensor disconnected, measure reference voltage at the harness connector. You should see approximately 5 volts from the ECM. If voltage is absent, trace the power supply wire for breaks or check ECM fuse integrity.

Step 4: Component Replacement If sensor resistance is out of specification or wiring shows damage, replace the faulty component. For used excavators, always apply dielectric grease to connector pins before reassembly to prevent future corrosion. Clear codes using diagnostic software and verify repair with a test cycle.

---

Disclaimer: This guide provides general troubleshooting information. Always consult the Hyundai service manual for your specific serial number and consider professional diagnosis for complex electrical issues or if you lack proper diagnostic equipment.