What is Hyundai HX220 NL EPFC Fault Code 1655 (1324-31)?

Fault Code 1655 (1324-31) indicates an Engine Speed/Position Sensor Circuit malfunction with a voltage above normal or shorted to high source. This code specifically relates to the crankshaft position sensor (CPS) or camshaft position sensor (CMS) circuit in the Hyundai HX220 NL EPFC excavator's electronic control system.

This diagnostic trouble code (DTC) signals that the Engine Control Module (ECM) has detected an abnormally high voltage reading from the engine speed/position sensor circuit—typically above 4.5-5.0 volts when normal operating range should be 0.5-4.5 volts. The crankshaft position sensor is critical for proper fuel injection timing, engine synchronization, and overall performance. When this sensor circuit fails, the ECM cannot accurately determine engine position or RPM, leading to potential engine shutdown or failure to start.

For the HX220 NL's Common Rail Diesel Engine, this sensor provides real-time data essential for precise fuel delivery and emissions control. Any disruption compromises engine efficiency and can trigger protective derate modes.

Common Symptoms

• Engine cranks but fails to start or experiences hard starting conditions
• Check Engine Light (CEL) or malfunction indicator lamp illuminated on the dashboard
• Sudden engine stalling during operation, particularly at idle or under load
• Rough idle, misfiring, or erratic RPM fluctuations when the engine does run
• Loss of engine power or activation of derate mode limiting machine performance to protect components

Potential Causes

The most frequent technical causes for Code 1655 (1324-31) in used Hyundai excavators include:

• Damaged or frayed sensor wiring harness, especially near the engine block where vibration and heat cause insulation breakdown
• Corroded or contaminated sensor connectors due to moisture ingress—common in machines with high operating hours
• Failed crankshaft or camshaft position sensor with internal short circuit to voltage supply
• Chafed wiring rubbing against engine components or frame rails (known issue on HX220 models near the timing cover)
• ECM internal fault or poor ground connections causing voltage reference errors
• Aftermarket sensor installation with incorrect voltage specifications or incompatible resistance values

How to Troubleshoot and Fix Code 1655 (1324-31)

Step 1: Visual Inspection Begin with a thorough inspection of the sensor wiring harness from the crankshaft/camshaft position sensor to the ECM connector. On used excavators, pay special attention to harness routing near the engine timing cover and starter motor where friction wear is common. Check for damaged insulation, exposed copper wire, or signs of previous repairs. Inspect the sensor connector for corrosion, bent pins, or oil contamination.

Step 2: Electrical Testing Using a digital multimeter (DMM), disconnect the sensor connector and measure resistance across the sensor terminals. Typical resistance values should be 200-1000 ohms (consult your service manual for exact specifications). Check for short to power by measuring voltage between each sensor wire and battery positive with ignition ON—any reading above 0.5V indicates a wiring short. Test harness continuity from sensor connector to ECM pins, ensuring less than 5 ohms resistance.

Step 3: Sensor and Voltage Supply Verification With the sensor connected and ignition ON (engine OFF), backprobe the sensor connector and measure supply voltage—should read approximately 5.0 volts from the ECM. Check the ground circuit for less than 0.1-volt drop to battery negative. If voltage reads above 5.5 volts consistently, suspect ECM failure or a short to a higher voltage source in the harness. For used machines, remove and inspect the sensor itself for metal debris accumulation, damaged reluctor wheel teeth, or incorrect air gap (typically 0.5-1.2mm).

Step 4: Component Replacement and Verification If wiring and voltage tests pass but the code persists, replace the crankshaft/camshaft position sensor with an OEM or quality aftermarket unit matching original specifications. After replacement, clear codes using Hi-ScanPro or compatible Hyundai diagnostic software, and perform a road test under load. On used excavators with over 5,000 hours, inspect the reluctor wheel or tone ring on the crankshaft for damage or missing teeth—a commonly overlooked issue causing intermittent high-voltage readings.

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Disclaimer: This guide provides general troubleshooting information for experienced technicians. Always consult the official Hyundai service manual for your specific machine serial number and software version. If you lack proper diagnostic tools or experience with high-voltage electrical systems, seek assistance from a certified Hyundai heavy equipment technician to avoid injury or further damage.