Coolant Temperature Sensor
2018 Jeep Wrangler · 3.6L V6
Sensor Type
thermistor
Waveform Type
dc-variable
Location
Front of engine block, below the throttle body, threaded into coolant passage near thermostat housing
Pins
2-pin connector
Timebase
1s/div or 5s/div for thermal changes
Voltage Scale
1V/div
Trigger
Not applicable for DC signal
Wiring
Tan/Yellow (signal to PCM) and Black/Light Blue (sensor ground)
Expected Voltage Range
At Idle
0.5V to 2V
At Higher RPM
0.5V to 2V
Expected Pattern
Smooth DC voltage that decreases as temperature increases, negative temperature coefficient thermistor
Known-Good Waveform
At cold start (68°F), voltage should read approximately 3.0-3.5V. As engine warms to operating temperature (195-220°F), voltage should smoothly decrease to 0.5-1.2V without jumps or spikes. Signal should be rock-steady with no noise.
Common Failure Patterns
Voltage reading stuck at 4.8-5.0V regardless of temperature
Cause: Open circuit in sensor or wiring, broken internal thermistor element
Voltage reading at 0V or near 0V
Cause: Short to ground in wiring or failed sensor internally shorted
Related DTCs: P0117
Diagnostic Tips
Pentastar 3.6L engines are known for coolant temperature sensor connector corrosion due to heat exposure. Always inspect connector for green corrosion and check pin tension. Verify voltage sweep from cold to hot follows smooth curve without steps.
Related Diagnostic Trouble Codes
P0115P0116P0117P0118P0119
Always confirm waveform data with your vehicle's OEM service manual before diagnosing.
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