Coolant Temperature Sensor
2017 Toyota Corolla · 1.8L I4
Sensor Type
thermistor
Waveform Type
dc-variable
Location
Front of engine block, below intake manifold, near thermostat housing on passenger side
Pins
2-pin connector
Timebase
1s/div
Voltage Scale
1V/div
Trigger
Not applicable for DC measurement
Wiring
Green wire (signal to ECM terminal THW), Black wire (sensor ground E2)
Expected Voltage Range
At Idle
0.3V to 0.7V
At Higher RPM
0.3V to 0.7V
Expected Pattern
Steady DC voltage that decreases as temperature increases, negative temperature coefficient thermistor
Known-Good Waveform
At cold start (68°F), expect approximately 2.0-2.5V. At full operating temperature (195°F), voltage should drop to 0.3-0.7V. The voltage should transition smoothly without sudden jumps as engine warms up, typically taking 5-10 minutes to reach stable operating voltage.
Common Failure Patterns
Voltage stuck at 4.8-5.0V regardless of temperature
Cause: Open circuit in sensor or wiring harness, broken sensor element
Voltage reads near 0V or fluctuates erratically
Cause: Short to ground in wiring or internal sensor short
Related DTCs: P0117
Voltage changes too slowly or reads incorrect temperature
Cause: Contaminated sensor tip, degraded thermistor, coolant leak affecting sensor
Related DTCs: P0128
Diagnostic Tips
Compare ECT reading with IAT at cold start - they should be within 10°F. On 2ZR-FE engine, verify 5V reference voltage at connector. Resistance should be approximately 2.3-2.7kΩ 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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