Coolant Temperature Sensor
1972 Dodge Challenger · 400ci V8
Sensor Type
thermistor
Waveform Type
dc-variable
Location
Screwed into intake manifold water jacket near thermostat housing
Pins
1-pin connector
Timebase
10s/div or DC measurement
Voltage Scale
1V/div
Trigger
Not applicable for DC measurement
Wiring
Single dark green wire; sensor grounds through case to engine block
Expected Voltage Range
At Idle
1.8V to 2.5V
At Higher RPM
0.5V to 1.2V
Expected Pattern
Smooth DC voltage that decreases as engine warms up, negative temperature coefficient thermistor
Known-Good Waveform
Cold engine (70°F) should read approximately 3.0-3.5V, warming to operating temperature (195°F) should show smooth decline to 1.8-2.2V. Voltage should decrease smoothly with no sudden jumps or dropouts as engine temperature rises. The 1972 Challenger uses a simple single-wire thermistor feeding the temperature gauge circuit.
Common Failure Patterns
Voltage stuck at 0.2V or below regardless of temperature
Cause: Sensor internally shorted or wire grounding out before sensor
Voltage stuck at 4.5V-5V regardless of temperature
Cause: Open circuit in sensor or wiring, loss of ground path
Erratic voltage jumping between ranges during warm-up
Cause: Corroded sensor threads causing intermittent ground connection
Diagnostic Tips
This era Mopar system has no ECM or DTCs. Test with ohmmeter: cold sensor should read 2000-3000 ohms, hot sensor 200-300 ohms. Verify good chassis ground as these single-wire sensors are very sensitive to poor grounding.
Related Diagnostic Trouble Codes
P0115P0116P0117P0118P0119
Always confirm waveform data with your vehicle's OEM service manual before diagnosing.
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