Coolant Temperature Sensor
2021 Toyota Camry · 2.5L I4 Hybrid
Sensor Type
thermistor
Waveform Type
dc-variable
Location
Mounted in the engine block coolant passage near the thermostat housing on the driver's side of the 2.5L A25A-FXS hybrid engine
Pins
2-pin connector
Timebase
1s/div or 5s/div for heat soak testing
Voltage Scale
1V/div
Trigger
N/A - DC signal
Wiring
Green/White wire (signal to ECM) and Brown wire (sensor ground)
Expected Voltage Range
At Idle
0.3V to 0.6V
At Higher RPM
0.3V to 0.6V
Expected Pattern
Smooth DC voltage that decreases as temperature increases; cold engine (20°C) shows ~3.0V, warm engine (80°C) shows ~0.5V, hot engine (95°C) shows ~0.3V
Known-Good Waveform
At cold start (20°C ambient), expect 2.5-3.5V that smoothly decreases to 0.4-0.6V as the engine reaches operating temperature (80-95°C). The voltage transition should be gradual over 5-10 minutes with no sudden jumps or dropouts. Hybrid system may cause frequent temperature fluctuations as the engine cycles on/off.
Common Failure Patterns
Voltage stuck at 4.5-5.0V regardless of temperature
Cause: Open circuit in sensor or wiring, broken sensor element
Voltage stuck near 0V or shows sudden drops to 0V
Cause: Short to ground in wiring or internal sensor short
Related DTCs: P0117
Erratic voltage readings or stepping pattern instead of smooth transition
Cause: Corroded connector pins or intermittent wiring connection, common at C12 ECM connector
Related DTCs: P0116
Diagnostic Tips
On hybrid models, the engine frequently shuts off and restarts, causing temperature fluctuations. Verify coolant level is correct as hybrid cooling system is more complex. Check for corrosion at the sensor connector which is exposed to road spray.
Related Diagnostic Trouble Codes
P0115P0116P0117P0118P0119
Always confirm waveform data with your vehicle's OEM service manual before diagnosing.
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