What is Hyundai HX220 NL EPFC Fault Code 4244 (4337-2)?

Fault Code 4244 (4337-2) indicates a malfunction in the hydraulic oil temperature sensor circuit, specifically reporting an abnormal voltage signal or open/short circuit condition in the transmission oil temperature monitoring system. This code is part of Hyundai's Electronic Power Flow Control (EPFC) system that continuously monitors hydraulic fluid temperatures to prevent overheating and component damage.

The hydraulic oil temperature sensor plays a critical role in the HX220 NL's performance management. When hydraulic fluid exceeds safe operating temperatures (typically above 95°C/203°F), the ECM (Engine Control Module) relies on this sensor data to implement protective measures. In used excavators, this sensor circuit is particularly vulnerable to degradation from years of exposure to heat, vibration, and moisture intrusion around the hydraulic tank area.

Common Symptoms

• Warning light illumination on the instrument panel, often accompanied by a temperature gauge reading abnormally high or low (pegged at minimum)
• Reduced hydraulic performance or automatic engine derate mode, limiting machine power output to 70-80% capacity
• Intermittent loss of hydraulic functions during extended operation, particularly swing or boom movements
• Error message display showing temperature-related alerts on machines equipped with advanced monitor systems
• Unusual hydraulic pump noise as the ECM attempts to compensate for perceived temperature issues

Potential Causes

The most common technical causes for Code 4244 in used HX220 NL excavators include:

• Corroded or loose electrical connectors at the sensor mounting point on the hydraulic tank (common failure point after 5,000+ operating hours)
• Damaged wiring harness between the sensor and ECM, particularly where the harness passes near the engine block or exhaust components
• Failed hydraulic oil temperature sensor due to internal resistance drift or moisture contamination
• Faulty ECM pins or internal circuit issues within the control module itself (less common but possible in high-hour machines)
• Poor ground connections at the sensor circuit, exacerbated by rust or paint buildup on mounting surfaces

How to Troubleshoot and Fix Code 4244 (4337-2)

Step 1: Visual Inspection and Connector Check Begin by locating the hydraulic oil temperature sensor on the side of the hydraulic tank. Disconnect the electrical connector and inspect for corrosion, bent pins, or moisture intrusion. Clean contacts with electrical contact cleaner and verify the connector locks securely. On used excavators, check for harness wear where cables contact frame members.

Step 2: Sensor Resistance Testing Using a digital multimeter, measure the sensor's resistance. At room temperature (20°C/68°F), resistance should typically read 2,000-3,000 ohms (consult your service manual for exact specifications). Compare readings with a temperature-resistance chart. If readings are out of specification or show infinite resistance (open circuit), replace the sensor.

Step 3: Circuit Voltage and Wiring Verification With the ignition on and sensor disconnected, check for 5-volt reference voltage at the harness connector using your multimeter. Trace the wiring from sensor to ECM, checking for shorts to ground, opens, or damaged insulation. Pay special attention to harness routing near hot engine components. Use Hyundai's Hi-MATE diagnostic software if available to monitor live sensor data and verify ECM communication.

Step 4: Ground Circuit Testing Verify continuity between the sensor ground pin and chassis ground (should read less than 1 ohm). Clean all ground connection points and apply dielectric grease to prevent future corrosion.

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Disclaimer: This guide provides general troubleshooting information. Always consult the official Hyundai service manual for your specific serial number. If you're uncomfortable performing electrical diagnostics, contact a certified Hyundai excavator technician to prevent further damage to electronic components.