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.
Outside Temperature Sensor
The outside temperature sensor function is to detect the vehicle's ambient temperature. It is necessary for the engine control module (ECM) to know the vehicle's ambient temperature so that the following can be controlled:
- the engine cooling fan (FC)
- The air conditioning (A/C) compressor's displacement.
The ambient temperature is also used as a substitute value in the event of certain faults or functions and to control certain diagnostic functions.
The temperature sensor is a resistor with negative temperature coefficient, so called NTC type. This is supplied with voltage from the control module.
The resistance in the sensor changes depending on the ambient temperature of the vehicle. This gives a signal between 0-5V to the engine control module (ECM). Low temperature results in high resistance (high voltage). High temperature in low resistance (low voltage). At -10 °C the resistance is approximately 10.7 MΩ, at 0 °C the resistance is approximately 6.3 MΩ and at 20 °C resistance is approximately 2.4 MΩ.
The outside temperature sensor is located in the left-hand door mirror.
The engine control module (ECM) can diagnose the outside temperature sensor. The sensor value can be read off using the diagnostic tool.
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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.