Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSINFINITI2002Q45 V8-4.5L (VK45DE)REPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTCOMPUTERS AND CONTROL SYSTEMSSENSORS AND SWITCHES - COMPUTERS AND CONTROL SYSTEMSCOOLANT TEMPERATURE SENSOR/SWITCH (FOR COMPUTER)DESCRIPTION AND OPERATION
2002 Infiniti Q45 V8-4.5L (VK45DE)
Coolant Temperature Sensor/Switch (For Computer): Description and Operation
2002 Infiniti Q45 V8-4.5L (VK45DE)SECTION Description and Operation
ENGINE COOLANT TEMPERATURE SENSOR (CIRCUIT)
COMPONENT DESCRIPTION
The engine coolant temperature sensor is used to detect the engine coolant temperature. The sensor modifies a voltage signal from the ECM. The modified signal returns to the ECM as the engine coolant temperature input. The sensor uses a thermistor which is sensitive to the change in temperature. The electrical resistance of the thermistor decreases as temperature increases.
CAUTION: Do not use ECM ground terminals when measuring input/output voltage. Doing so may result in damage to the ECM's transistor. Use a ground other than ECM terminals, such as the ground.
RADIATOR COOLANT TEMPERATURE SENSOR (CIRCUIT)
COMPONENT DESCRIPTION
The radiator coolant temperature sensor is installed on the radiator lower tank and used to detect the radiator coolant temperature. The sensor modifies a voltage signal from the ECM and returns the modified signal to the ECM as the radiator coolant temperature input. The sensor uses a thermistor which is sensitive to the change in temperature. The electrical resistance of thermistor decreases as temperature increase. The ECM uses this signal to control the cooling fan speed control solenoid valve.
CAUTION: Do not use ECM ground terminals when measuring input/output voltage. Doing so may result in damage to the ECM's transistor. Use a ground other than ECM terminals, such as the ground.
Reference Data:
COMPONENT DESCRIPTION
The engine coolant temperature sensor is used to detect the engine coolant temperature. The sensor modifies a voltage signal from the ECM. The modified signal returns to the ECM as the engine coolant temperature input. The sensor uses a thermistor which is sensitive to the change in temperature. The electrical resistance of the thermistor decreases as temperature increases.
CAUTION: Do not use ECM ground terminals when measuring input/output voltage. Doing so may result in damage to the ECM's transistor. Use a ground other than ECM terminals, such as the ground.
RADIATOR COOLANT TEMPERATURE SENSOR (CIRCUIT)
COMPONENT DESCRIPTION
The radiator coolant temperature sensor is installed on the radiator lower tank and used to detect the radiator coolant temperature. The sensor modifies a voltage signal from the ECM and returns the modified signal to the ECM as the radiator coolant temperature input. The sensor uses a thermistor which is sensitive to the change in temperature. The electrical resistance of thermistor decreases as temperature increase. The ECM uses this signal to control the cooling fan speed control solenoid valve.
CAUTION: Do not use ECM ground terminals when measuring input/output voltage. Doing so may result in damage to the ECM's transistor. Use a ground other than ECM terminals, such as the ground.
RENDER: 1.0x
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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.