The oxygen (O2) sensors on a Honda Accord are designed to measure the amount of oxygen in the exhaust gas before and after the catalytic converter. The primary oxygen sensor is located in the exhaust manifold and the secondary is located in the exhaust pipe, just behind the catalytic converter. When these sensors fail, the powertrain control module (PCM) cannot determine the amount of oxygen present in the exhaust and has trouble adjusting the fuel injectors to achieve an optimum air-to-fuel ratio. Replacement O2 sensors are available from auto parts stores and Honda dealerships.
Place the Accord's gear selector in the "P" position and shut off the engine. Apply the parking brake and open the hood. Disconnect the negative battery lead from the battery terminal using a battery terminal wrench.
Raise the front of the vehicle with an automotive jack and support it with jack stands. Chock the rear wheels.
Locate the cast-iron exhaust manifold on the front of the engine. Look at the base of the exhaust manifold, just above the exhaust pipe. The primary oxygen sensor screws into the bottom of the manifold and has a single-wire electrical connector attached to it.
Crawl underneath the vehicle and locate the secondary oxygen sensor. It screws into the exhaust pipe, just behind the catalytic converter. It has a single-wire electrical connector attached to it.
