What is Caterpillar Fault Code EID1568?

Caterpillar Fault Code EID1568 indicates an Engine Coolant Temperature (ECT) Sensor Circuit High Voltage condition detected by the Electronic Control Module (ECM). This diagnostic trouble code triggers when the ECM receives a voltage signal from the coolant temperature sensor that exceeds the manufacturer's specified upper threshold, typically above 4.8-5.0 volts.

The ECT sensor plays a critical role in Caterpillar excavators by monitoring engine coolant temperature and sending this data to the ECM. The ECM uses this information to adjust fuel injection timing, control the cooling fan, and manage engine protection strategies. When EID1568 is active, the ECM cannot accurately determine engine temperature, which can lead to improper fuel delivery, inefficient combustion, and potential engine damage from overheating or overcooling conditions.

Common Symptoms

When Code EID1568 is active on your Caterpillar excavator, you may experience:

• Check Engine Light or warning lamp illuminated on the instrument cluster
• Engine running in derate mode or reduced power output to protect components
• Hard starting or extended cranking times, especially in cold conditions
• Rough idle or irregular engine performance during warm-up
• Cooling fan running continuously at high speed regardless of actual engine temperature

Potential Causes

The most common technical causes for EID1568 in used Caterpillar excavators include:

• Open circuit in the ECT sensor wiring harness due to wire breakage or corrosion
• Failed ECT sensor with internal circuit degradation (common in high-hour machines)
• Damaged connector pins or corroded terminals at the sensor or ECM connection points
• Harness chafing at known rub points near the engine block or coolant crossover tubes
• ECM internal fault (rare, but possible in older excavators with high operating hours)
• Poor ground connection affecting sensor circuit reference voltage

How to Troubleshoot and Fix Code EID1568

Step 1: Visual Inspection Begin by inspecting the ECT sensor and its wiring harness for obvious damage. The sensor is typically located near the thermostat housing or cylinder head. Check for corroded connectors, damaged wire insulation, or evidence of coolant leaks near the sensor that could cause corrosion. On used excavators, pay special attention to harness routing where wires contact metal surfaces or engine components.

Step 2: Electrical Testing Disconnect the ECT sensor connector and use a digital multimeter to measure resistance across the sensor terminals. Compare readings against Caterpillar specifications (typically 2,000-3,000 ohms at room temperature). Next, check for open circuits by measuring continuity from the sensor connector to the ECM. Resistance should be less than 5 ohms. Also verify the 5-volt reference supply from the ECM at the sensor connector.

Step 3: Advanced Diagnostics Connect Caterpillar Electronic Technician (Cat ET) diagnostic software to monitor live sensor data. If voltage reads constantly at 5.0V, suspect an open sensor circuit. Inspect connectors for bent pins or corrosion, particularly the ECM connector which experiences vibration wear. If all wiring checks out, replace the ECT sensor with a genuine Caterpillar part, as aftermarket sensors often cause recurring codes.

Disclaimer: This guide provides general troubleshooting information. Always consult your machine's service manual and consider engaging a certified Caterpillar technician for complex electrical diagnostics and repairs.