Coolant Temperature Sensor:

PCM Wiring:

COOLANT SENSOR OPERATION
The Engine Coolant Temperature (ECT) sensor is a thermistor (a resistor which varies its resistance value based on temperature) mounted in the engine coolant stream. The coolant sensor is a two wire component which receives a reference voltage signal from the Powertrain Control Module (PCM). Low coolant temperature produces a high resistance, while a high temperature produces low resistance. The PCM supplies a voltage signal to the coolant sensor through a resistor in the PCM and measures the signal voltage output. The voltage will be high when the engine is cold, and the voltage will be low when the engine is hot.

PCM INPUT
The sensor provides coolant temperature information to the PCM for fuel enrichment, ignition timing, EGR operation, canister purge control, air management, idle speed control, and closed loop fuel control.

TROUBLE CODES
A failure in the coolant sensor circuit should set either a Trouble Code P014 or code P015. An intermittent problem in the coolant sensor circuit can set a code P073.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

Coolant Temperature Sensor/Switch (For Computer): Description and Operation