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.
PREMAIR Sensor (2006-)
The function of the Premair sensor is to meet legal requirements for low emission variants. The sensor is located on the radiator.
The sensor measures the temperature of the radiator and transmits the value, together with a check of its own condition, to the Engine control module (ECM). During the engine's warm-up phase the Engine control module (ECM) carries out a number of checks of the received information in order to determine the status of the sensor and the radiator.
The sensor communicates with the Engine control module (ECM) via LIN (Local Interconnect Network)communication, a standardized serial communication method. Transmitted information is encrypted.
The Premair sensor is diagnosed by the Engine control module (ECM). The sensor is secured to the radiator and cannot be replaced separately.
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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.