What is Yanmar General Fault Code P0119-2?

Fault Code P0119-2 indicates an intermittent signal issue with the Engine Coolant Temperature (ECT) sensor circuit. This code is triggered when the Engine Control Module (ECM) detects erratic or unstable voltage readings from the ECT sensor that fall outside expected parameters but haven't completely failed.

In Yanmar diesel engines, the ECT sensor plays a critical role in fuel injection timing, cold start enrichment, and emission control strategies. The "-2" suffix specifically denotes an intermittent or irregular circuit condition rather than a complete sensor failure. This means the signal is cutting in and out, providing unreliable data that can confuse the ECM and compromise engine performance. For used excavators, this code often signals aging electrical connections or sensor degradation that requires immediate attention to prevent engine protection modes or inefficient operation.

Common Symptoms

• Check Engine Light illuminates on the instrument panel, potentially with reduced engine power
• Difficult cold starting or extended cranking time before the engine fires
• Irregular idle speed or engine hunting, especially when the engine is warming up
• Poor fuel economy due to incorrect fuel mixture calculations
• Engine derate mode may activate if the ECM cannot reliably determine coolant temperature

Potential Causes

The intermittent nature of P0119-2 in used Yanmar excavators typically stems from:

• Corroded or loose electrical connections at the ECT sensor connector, common in machines exposed to moisture and debris
• Damaged wiring harness due to rubbing against engine components or frame members during operation
• Failing ECT sensor with internal resistance issues that cause intermittent signal dropout
• Contaminated connector pins from oil seepage or coolant intrusion near the sensor location
• Poor ground connection at the ECM or sensor ground circuit
• Age-related deterioration of the sensor's internal thermistor element

How to Troubleshoot and Fix Code P0119-2

Step 1: Visual Inspection Begin by locating the ECT sensor (typically threaded into the engine block or thermostat housing). Carefully inspect the wiring harness from sensor to ECM for obvious damage, chafing, or wear points. Check the sensor connector for corrosion, bent pins, or moisture intrusion—common issues in used equipment.

Step 2: Electrical Testing Using a digital multimeter, check the ECT sensor resistance at various temperatures (consult Yanmar specifications, typically 2-3kΩ at 20°C). Test the circuit voltage at the ECM connector with the sensor disconnected—you should see approximately 5 volts reference voltage. Check for continuity in the signal and ground wires.

Step 3: Monitor Live Data If available, use Yanmar diagnostic software or a compatible scan tool to monitor real-time ECT sensor values. Watch for sudden spikes, dropouts, or implausible readings while wiggling the harness and connector—this confirms intermittent connections.

Step 4: Repair or Replace For used excavators, clean all connector terminals with electrical contact cleaner and apply dielectric grease to prevent future corrosion. Repair any damaged wiring with proper gauge wire and heat-shrink connections. If the sensor tests out of specification or shows erratic resistance values, replace the ECT sensor with a genuine Yanmar part to ensure proper calibration.

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Disclaimer: This guide provides general troubleshooting information. Always consult the official Yanmar service manual for your specific model and consider professional diagnostic assistance for complex electrical issues.