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Replacing the Lambda Sensor in the Exhaust Gas Circuit

Model: BMW Serie 3 E36 - Years 1990-2001
Part: Oxygen sensor

The lambda sensor is a device that monitors the pollutants in the exhaust gases to maintain the air-fuel ratio (kg air/kg fuel) within the optimal efficiency range of the catalytic converter. The output signal from the sensor is an electrical signal sent to the fuel injector control unit. The lambda sensor should be replaced frequently, especially if there is a loss of power, excessive fuel consumption, or pollutant exhaust gases. An effective check of the four lambda sensors can be done with specialized equipment, but a simple check can be performed using a good digital multimeter. Disconnect the sensor connector and check the electrical resistance by measuring between the white wire and the yellow wire. If the sensor shows some resistance, it can be considered functional; otherwise, the sensor is faulty. Check all four sensors, two of which are located in the exhaust manifold and two in the engine manifold. Due to high temperatures, replace the sensors when the engine is very cold. Using a simple wrench, unscrew the sensor and disconnect the connector. For safety, replace all sensors, then drive several miles and retest with the appropriate equipment to verify the return of pollutant parameters.

Updated on 2 February 2026 by ScegliAuto

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