Case CX220C Fault Code 117: Complete Diagnostic Guide

What is Case CX220C Fault Code 117?

Case CX220C Fault Code 117 indicates an Engine Coolant Temperature (ECT) Sensor Circuit High Voltage condition. This diagnostic trouble code triggers when the Engine Control Module (ECM) detects an abnormally high voltage signal from the coolant temperature sensor circuit, typically above 4.8-4.9 volts.

The ECT sensor is a critical thermistor-type component that monitors engine operating temperature in the Case CX220C's Isuzu engine. This sensor provides real-time data to the ECM for fuel injection timing, idle speed control, and engine protection strategies. When Code 117 activates, the ECM switches to default temperature values, which can significantly impact engine performance and fuel efficiency on used machines where precise temperature management becomes even more crucial due to potential cooling system degradation.

Common Symptoms

When Code 117 is active on your Case CX220C, you may experience:

• Check Engine Light or malfunction indicator illuminated on the instrument cluster
• Hard starting conditions, especially when the engine is warm (ECM assumes cold engine mode)
• Rough idle or poor throttle response due to incorrect fuel mapping
• Cooling fan running continuously at high speed regardless of actual engine temperature
• Black smoke from exhaust caused by overly rich fuel mixture from faulty temperature readings

Potential Causes

The most common technical failures triggering Code 117 on used Case CX220C excavators include:

• Open circuit in sensor wiring harness – particularly common where harness routes near the valve cover or exhaust manifold on high-hour machines
• Corroded or damaged ECT sensor connector – moisture intrusion at the two-pin connector causes intermittent high resistance
• Failed coolant temperature sensor – internal thermistor element breaks open, creating infinite resistance
• Damaged sensor ground circuit – poor ground connection at G102 ground point near ECM mounting location
• Chafed wiring at known rub points behind the engine, especially where harness contacts engine mounts or brackets
• ECM internal fault – rare but possible on machines with 8,000+ operating hours

How to Troubleshoot and Fix Code 117

Step 1: Visual Inspection Begin with a thorough inspection of the ECT sensor connector located on the engine block near the thermostat housing. Disconnect the two-pin connector and examine both male and female terminals for corrosion, bent pins, or moisture. On used excavators, this connector frequently shows green corrosion due to coolant weeping. Clean contacts with electrical contact cleaner and dielectric grease.

Step 2: Sensor Resistance Testing Using a digital multimeter (DMM), measure resistance across the ECT sensor terminals with the sensor disconnected. At 68°F (20°C), you should read approximately 2,300-2,700 ohms. At 176°F (80°C), resistance should drop to 270-330 ohms. An open circuit (infinite resistance) confirms sensor failure. Check your Case service manual for exact specifications, as tolerances vary by production year.

Step 3: Wiring Harness Verification With the sensor disconnected and ignition ON (engine OFF), measure reference voltage at the harness connector. You should see approximately 5 volts on the signal wire. If voltage reads above 4.9 volts continuously, inspect the sensor ground wire (typically black or black/white) for continuity to chassis ground. Check for harness damage along the routing path from sensor to ECM, paying special attention to areas where the harness passes through metal grommets or contacts vibrating components—common wear points on machines with 5,000+ hours.

Step 4: Advanced Diagnostics If sensor and wiring test satisfactorily, connect Case diagnostic software (ServiceMaster or equivalent) to monitor live ECT sensor data. Compare readings with an infrared thermometer measurement of actual coolant temperature. A discrepancy greater than 10°F indicates ECM processing issues. Before condemning the ECM, verify all ground connections at the ECM mounting bracket are clean and tight—corrosion here frequently causes erratic sensor readings on older machines.

Disclaimer: This guide provides general diagnostic procedures for Case CX220C excavators. Always consult the manufacturer's official service manual for complete specifications and safety procedures. If you're uncomfortable performing electrical diagnostics, consult a certified Case dealer or qualified heavy equipment technician to prevent misdiagnosis and unnecessary parts replacement.