What is Hyundai HX220 NL EPFC Fault Code 693 (1172-2)?

Fault Code 693 (1172-2) indicates a malfunction in the Engine Coolant Temperature (ECT) Sensor Circuit – specifically a voltage signal that is too low or an intermittent short to ground. This code is triggered when the Engine Control Module (ECM) detects that the coolant temperature sensor is sending voltage readings below the expected threshold, typically below 0.5 volts for an extended period.

In the Hyundai HX220 NL EPFC excavator, the ECT sensor plays a critical role in engine management. It informs the ECM about operating temperatures, which directly affects fuel injection timing, idle speed, and emission controls. When this sensor circuit fails, the ECM cannot accurately regulate engine performance, potentially leading to poor fuel economy, rough idling, or even engine protection shutdowns during heavy work cycles.

Common Symptoms

When Code 693 (1172-2) is active on your HX220 NL, operators typically experience:

• Check Engine Light or malfunction indicator illuminated on the dashboard
• Hard starting or extended cranking time, especially in cold conditions
• Rough idle or unstable RPM fluctuations when the machine is warming up
• Black or white smoke from the exhaust due to incorrect fuel mixture compensation
• Engine derate mode activation, limiting power output to protect engine components

Potential Causes

The most common technical causes for this fault code in used HX220 NL excavators include:

• Damaged or corroded ECT sensor connector – especially common in machines with high operating hours in wet or muddy conditions
• Shorted or chafed wiring harness between the sensor and ECM, often occurring at harness routing points near the engine block
• Failed coolant temperature sensor – internal sensor element degradation over time
• Low coolant level exposing the sensor tip and causing erratic readings
• ECM internal circuit failure – rare but possible in older machines with electrical system stress
• Corroded ground connections affecting the sensor's reference voltage circuit

How to Troubleshoot and Fix Code 693 (1172-2)

Step 1: Visual Inspection Begin by inspecting the ECT sensor located on the engine block near the thermostat housing. Check for coolant leaks, corrosion on the electrical connector, and damaged pins. On used excavators, carefully examine the wiring harness for signs of rubbing against the engine or frame – this is a common failure point on the HX220 NL after 5,000+ operating hours.

Step 2: Electrical Testing Using a digital multimeter, disconnect the ECT sensor connector and measure resistance across the sensor terminals. At 68°F (20°C), resistance should read approximately 2,000-3,000 ohms (consult your service manual for exact specifications). Next, check for continuity between the sensor ground wire and chassis ground. Measure voltage at the ECM connector – you should see approximately 5 volts reference voltage on the signal wire with the sensor disconnected.

Step 3: Harness and Ground Verification Inspect all ground points in the engine electrical system. Clean and tighten connections, as corrosion in ground circuits is particularly problematic in used machines. Use the Hi-SCAN Pro diagnostic tool or equivalent Hyundai diagnostic software to monitor live ECT sensor data while wiggling harness connections – intermittent voltage drops indicate damaged wiring.

Step 4: Component Replacement If testing confirms sensor failure, replace the ECT sensor with a genuine Hyundai part (part number specific to HX220 NL EPFC). When installing, apply dielectric grease to connector terminals to prevent future corrosion. Clear fault codes and perform a test cycle under load to verify repair.

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