Case CX210C Fault Code 606: Complete Diagnostic Guide

What is Case CX210C Fault Code 606?

Fault Code 606 on the Case CX210C excavator indicates a High Signal Voltage Error in the Engine Coolant Temperature (ECT) Sensor Circuit. This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) detects a voltage reading above the normal operating range (typically above 4.8-4.9 volts) from the coolant temperature sensor circuit.

The ECT sensor plays a critical role in engine management by monitoring coolant temperature and sending this data to the ECM. This information directly influences fuel injection timing, idle speed, and engine protection protocols. On used Case CX210C machines, this code can significantly impact engine performance and may trigger protective derate modes that limit machine productivity.

Common Symptoms

When Code 606 is active on your Case CX210C, operators typically experience:

• Check Engine Light or warning lamp illuminated on the instrument cluster
• Engine derate mode activated, limiting maximum RPM and hydraulic performance
• Hard starting or rough idle, especially when the engine is cold
• Default temperature reading displayed on the monitor (often showing maximum temperature)
• Cooling fan running continuously at high speed, regardless of actual engine temperature

Potential Causes

The most common technical reasons for Code 606 on used CX210C excavators include:

• Open circuit in the ECT sensor wiring harness due to wire breakage or connector separation
• Failed ECT sensor with internal open circuit (common failure mode in high-hour machines)
• Corroded or damaged connector pins at the sensor or ECM connection points
• Wiring harness chafing near the engine block or frame rails (known wear point on this model)
• ECM internal fault affecting the 5-volt reference circuit (less common)
• Aftermarket sensor installation with incorrect resistance specifications

How to Troubleshoot and Fix Code 606

Step 1: Visual Inspection Begin with a thorough inspection of the ECT sensor located on the engine block near the thermostat housing. Check for physical damage, coolant leaks, or corrosion on the two-pin connector. On used excavators, pay special attention to harness routing where wires contact metal surfaces—this is a common failure point.

Step 2: Electrical Testing Disconnect the ECT sensor connector and use a digital multimeter to measure resistance across the sensor terminals. At room temperature (68°F/20°C), resistance should read approximately 2,400-2,700 ohms. If the reading shows infinite resistance (OL), the sensor has an internal open circuit and requires replacement.

Step 3: Circuit Verification With the sensor disconnected, check for 5-volt reference voltage at the harness connector (key on, engine off). Measure continuity between the signal wire and ECM pin, and between the ground wire and chassis ground. Resistance should be below 5 ohms. High resistance indicates corroded connections or damaged wiring.

Step 4: Repair and Clear Code Replace the faulty sensor with an OEM-equivalent part meeting Case specifications. Apply dielectric grease to connector pins to prevent future corrosion. After repairs, clear the code using Case diagnostic software or a compatible scan tool, then perform a test cycle to verify the fix.

---

Disclaimer: This guide provides general diagnostic information for Code 606. Always consult the official Case service manual and consider professional diagnostic assistance for complex electrical issues or if you lack proper testing equipment.