Replace the Upstream Oxygen Sensor

Replacing a failed upstream oxygen sensor is necessary to restore accurate air-fuel mixture control by the PCM. Follow these steps to perform the replacement:

1. Ensure the engine is completely cool to prevent burns. Locate the upstream oxygen sensor, which is typically found in the exhaust manifold or the exhaust pipe ahead of the catalytic converter.
2. Disconnect the electrical connector by depressing the release tab and pulling the plug apart.
3. Use a specialized oxygen sensor socket and a ratchet to unscrew the old sensor from the exhaust pipe.
4. Apply a small amount of anti-seize compound to the threads of the new sensor, being careful not to get any on the sensor tip.
5. Thread the new sensor into the exhaust by hand to ensure it is not cross-threaded, then tighten it to the manufacturer's specified torque using the sensor socket.
6. Reconnect the electrical harness until it clicks securely into place.
7. Clear any stored fault codes from the PCM using an OBD-II scan tool.
8. Start the engine and allow it to reach normal operating temperature. Use your scan tool to monitor live data; confirm the sensor voltage now oscillates rapidly between 0.1V and 0.9V.

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