What is Kato HD820V Fault Code P1572?

Fault Code P1572 on the Kato HD820V excavator indicates a malfunction in the Engine Coolant Temperature (ECT) Sensor Circuit - High Input. This diagnostic trouble code (DTC) is triggered when the Engine Control Module (ECM) detects an abnormally high voltage signal from the coolant temperature sensor, typically above 4.8 volts, suggesting an open circuit, damaged sensor, or wiring issue.

The ECT sensor plays a critical role in engine management by monitoring coolant temperature and sending real-time data to the ECM. This information directly influences fuel injection timing, idle speed control, and engine protection protocols. On used Kato HD820V excavators, this code is particularly concerning because improper coolant temperature readings can lead to poor fuel economy, hard starting conditions, and potential engine overheating without proper warning systems activating.

Common Symptoms

When Code P1572 is active on your Kato HD820V, operators typically experience:

• Check Engine Light or malfunction indicator lamp illuminated on the dashboard
• Hard starting or extended cranking time, especially in cold weather conditions
• Rough idle or erratic engine RPM fluctuations during warm-up
• Poor fuel efficiency and black smoke from exhaust due to incorrect fuel mixture
• ECM defaulting to a fixed temperature value (typically around 80°C/176°F), affecting overall engine performance

Potential Causes

The most common technical causes for P1572 in used Kato HD820V excavators include:

• Open circuit in the ECT sensor wiring harness, often caused by wire chafing near the engine block mounting points
• Faulty ECT sensor with internal resistance breakdown (common in machines with 5,000+ operating hours)
• Corroded or loose electrical connectors at the sensor or ECM terminals due to moisture intrusion
• Damaged wiring insulation from engine heat exposure or rodent damage in stored equipment
• ECM internal fault (rare, but possible in older units with voltage spike history)

How to Troubleshoot and Fix Code P1572

Step 1: Visual Inspection Begin by locating the ECT sensor (typically mounted on the engine block near the thermostat housing). Inspect the wiring harness from sensor to ECM for obvious damage, abrasion points where the harness contacts metal surfaces, or signs of heat degradation. On used excavators, pay special attention to connector pins for corrosion or bent terminals.

Step 2: Electrical Testing Disconnect the ECT sensor connector and use a digital multimeter to measure resistance across the sensor terminals. At room temperature (20°C/68°F), resistance should typically read between 2,000-3,000 ohms (consult your Kato service manual for exact specifications). If the reading shows infinite resistance (open circuit) or zero ohms (short circuit), replace the sensor.

Step 3: Circuit Voltage Check With the sensor disconnected and ignition on (engine off), measure voltage at the harness connector leading to the sensor. You should see approximately 5 volts on the signal wire. If voltage reads above 4.9 volts continuously, this confirms the high input condition. Check for open circuits in the ground wire or signal wire breaks.

Step 4: Connector and Harness Repair For used machinery, closely examine connector housings for moisture intrusion or terminal corrosion. Clean contacts with electrical contact cleaner and apply dielectric grease before reconnection. Repair any wire insulation damage with heat-shrink tubing rated for engine compartment temperatures.

Step 5: Clear Code and Test After repairs, clear the fault code using Kato diagnostic software or a compatible OBD scanner. Run the engine through a complete warm-up cycle while monitoring live coolant temperature data to verify the sensor is reading accurately across the temperature range.

---

Disclaimer: This guide provides general troubleshooting information for Code P1572. Always consult the official Kato HD820V service manual and consider professional diagnostic assistance for complex electrical issues or if you're unfamiliar with excavator electrical systems.