Coolant Temperature Sensor
2019 Hyundai Tucson · 2.5L I4
Sensor Type
thermistor
Waveform Type
dc-variable
Location
Mounted on the driver side of the cylinder head, near the thermostat housing, facing the firewall
Pins
2-pin connector
Timebase
10s/div for warm-up monitoring
Voltage Scale
1V/div
Trigger
Not applicable for DC signal
Wiring
Yellow/Green wire (signal to ECM) and Black wire (sensor ground)
Expected Voltage Range
At Idle
0.4V to 0.8V
At Higher RPM
0.3V to 0.6V
Expected Pattern
Smooth declining DC voltage as engine warms from cold start (4.5V at -40°C to 0.5V at 100°C), negative temperature coefficient thermistor
Known-Good Waveform
At cold start (68°F/20°C), expect approximately 2.5-3.0V that smoothly decreases to 0.5-0.7V as engine reaches operating temperature (195°F/90°C). The voltage decline should be gradual and linear without sudden jumps or drops, taking approximately 5-8 minutes to reach normal operating temperature.
Common Failure Patterns
Voltage stuck at 4.5-5.0V regardless of engine temperature
Cause: Open circuit in sensor element or wiring harness break
Voltage reads 0V or near 0V constantly
Cause: Short to ground in wiring or internal sensor short
Related DTCs: P0117
Diagnostic Tips
Use a heat gun to test sensor response - voltage should drop smoothly as temperature increases. These Smartstream 2.5L engines are prone to coolant leaks at the sensor causing corrosion; always inspect the connector for green corrosion and test resistance (10kΩ at 68°F).
Related Diagnostic Trouble Codes
P0115P0116P0117P0118P0119
Always confirm waveform data with your vehicle's OEM service manual before diagnosing.
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