How do you replace the O2 sensor on a 1999 civic OBD code P0135 bank 1- sensor 1?

Answer 1

When you open the hood, the primary heated o2 sensor is located on the exhaust manifold toward the hood latch. You'll need a special socket to remove it. It looks like a normal deep wall socket, but it has a slot on it to allow the wire to pass through it.

Disconnect the battery and allow the engine to cool off completely before starting this process.

Before attempting to unscrew it, follow the wire to the connection about 12 inches to the left. Push the latch to release it, the other side of the wire comes loose. The part of the connection that is attached to the sensor is attached to the plug mount. Slip a small screwdriver under it to release it. Remove the sensor from the harness to get it out. The new sensor should have some anti-seize lube in it, if it doesn't put some on the threads and screw the new one in. If your new sensor has a longer wire than the original one, you'll need to use the provided wire ties to remove the slack. Loop the excess wire so that it doesn't risk coming in contact with any moving parts or the exhaust manifold.

Depending on if you've let the car sit long enough without the battery connected, you may have to reset the computer (clear the code) in order to get rid of the check engine light.