A Honda Civic has two sensors that read oxygen levels in the exhaust when the engine is running. The oxygen level data is used by a Honda Civic’s computer to control fuel delivery and ignition. Located upstream and downstream of the catalytic converters, the sensors can malfunction and cause the engine to lose power. A bad oxygen sensor can result in an engine light that indicates something needs to be fixed, a malfunctioning engine that blows smoke out of the tailpipe, fails an emissions test or doesn’t run at all. Change an oxygen sensor on a Honda Civic using an oxygen sensor socket and some penetrating oil.
Apply penetrating oil around the base of the faulty oxygen sensor where it threads into the exhaust pipe or exhaust manifold. The Honda Civic has two sensors that monitor the exhaust gases produced by the engine during operation. One sensor is located before the catalytic converter and the other after it. The one upstream can be found by removing the exhaust manifold and the other outside the exhaust near the mufflers. Depending on which sensor is bad, you’ll either be working inside the engine compartment or underneath the vehicle.
Disconnect one oxygen sensor from the wiring harness at the wiring adapter that holds it in place. The wiring adapter has a tab that locks two connectors together, and needs to be unlocked to separate the sensor connector from the harness connector. Lift the tab and separate the adapters. The sensor and its cable can be removed without twisting the harness wires as the sensor rotates inside the threaded collar when removed.
Place an oxygen sensor socket over the top of the sensor. These connectors have a space for the sensor cable to pass through the side of the socket, allowing the socket to be placed around the sensor and the sensor to be loosened from its position on the sensor mounting collar. Rotate the socket counterclockwise to loosen the sensor into its threaded mounting collar.
Disconnect the socket from the entire sensor when it has loosened enough to remove it by hand, or continue turning the socket and sensor counterclockwise until it is free of the threaded collar that holds it in place.
Remove the sensor and discard it properly. Oxygen sensors use precious metals to read oxygen levels in the exhaust gas. These sensors must be properly recycled.
Insert a new oxygen sensor into the threaded sensor collar by hand until tight. Place the sensor connector on top of the new sensor, and use the ratchet wrench to further tighten it. When the sensor has been tightened securely, plug the new sensor into the old wiring harness using the new sensor wiring adapter.
Tips
On hard-to-remove sensors, use a torch to gently heat the threaded collar where the sensor is located to help loosen it for removal. The heat will expand the collar enough to allow the sensor threads to break free from the threaded collar. If you don’t have a torch, run the vehicle at its operating temperature.
Warnings
A Honda Civic exhaust will be very hot if you run the vehicle before changing the oxygen sensors. Because most sensors are difficult to remove, heat is usually applied to obtain their release. When heat is added to the exhaust, it becomes hot enough to burn the skin long after the heat has been applied. Avoid burns by wearing gloves and protective clothing.