How to Wire a Bosch O2 Sensor


Vehicle oxygen (O2) sensors are connected in the engine's exhaust system, allowing the engine control unit (ECU) to monitor the exhaust gases for fuel tuning and emissions purposes. Most vehicles are equipped with a primary and secondary O2 sensor, installed into the exhaust system before and after the catalytic converter. Since the O2 sensors must operate in the extreme heat of the exhaust flow, they are prone to breaking down on high-mileage vehicles. Bosch manufactures universal replacement O2 sensors that wire directly in place of malfunctioning stock units.

Things You'll Need

  • Bosch O2 sensor
  • Floor jack
  • Jack stands
  • 22 mm open-end wrench
  • Wire cutters
  • Park your vehicle on a solid, flat surface. Disconnect the vehicle battery cables, located in the engine bay. This is to ensure user safety when working with the O2 sensor wiring. Also, wait for your vehicle to thoroughly cool before you begin installation of the Bosch O2 sensor, as the exhaust system will be extremely hot after driving.

  • Raise the front of your vehicle with a floor jack, and support the chassis on jack stands. Search along the exhaust system underneath your vehicle to find the O2 sensor you wish to replace. Primary O2 sensors will be connected into either the exhaust manifold piping at the head of the exhaust system, or into the front-end of the catalytic converter at the exhaust manifold outlet. Secondary O2 sensors are connected into the rear-end of the catalytic converter piping.

  • Use a 22 mm open-end wrench to remove the O2 sensor from the exhaust piping. The opposite end of the O2 sensor is wired into the ECU harness. Midway along the O2 wiring is a plastic plug by which it connects into the ECU wiring. Undo this plug connection, and remove the O2 sensor.

  • Lay the stock O2 sensor parallel to the Bosch sensor to compare wire lengths. Cut the plastic plug off of the stock O2 sensor, leaving enough wiring connected to the plug to allow for an equal-length assembly of the Bosch O2 sensor when compared to the stock unit.

  • Refer to vehicle-specific wiring diagrams to ensure that you splice the stock plug wires onto the proper Bosch O2 sensor wires. Use wire strippers to strip approximately 10 mm of insulation from the stock O2 plug wires. Use the supplied Bosch wire color table to match the stock O2 sensor plug wires to the Bosch O2 sensor wires. Connect the plug to the O2 sensor by splicing the appropriate wires via the supplied Bosch crimping and insulation kit. The Bosch wire crimps can be secured by pulling at either end of the locking crimp. The Bosch insulation collar will then clip over top of the wire splices, ensuring proper wiring protection.

  • Install the Bosch O2 sensor in place of the stock unit by the opposite procedure of removal. With the stock plug attached, the Bosch O2 sensor will be a direct plug-in replacement. Install the supplied O2 sensor gasket onto the Bosch O2 sensor before threading it into the exhaust piping. Be careful when tightening the O2 sensor hex collar so that you don't damage the O2 sensor wiring connection.

  • Remove the jack stands from under your vehicle, and lower it with a floor jack. If your vehicle was displaying a "check engine" light due to the malfunctioning O2 sensor, the light should disable by itself after a few normal driving sessions with your new Bosch sensor installed.

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