This procedure covers the removal and replacement of the downstream oxygen sensor (Sensor 2) located after the catalytic converter on the 2018-2024 Honda Accord 1.5L Turbo engine.

Warnings

Tools required

Parts

• Downstream oxygen sensor (Sensor 2) × 1 — Use OEM Honda part or compatible aftermarket

Preparation

1. Allow the exhaust system to cool completely if vehicle was recently operated (minimum 1 hour)
2. Park vehicle on level ground and apply parking brake
3. Place wheel chocks behind rear wheels
4. Raise the front of vehicle using a floor jack and support securely on jack stands
5. Locate the downstream O2 sensor positioned after the catalytic converter in the exhaust system
6. Verify replacement sensor matches the old sensor connector type and thread pitch

Procedure

1. 1

   Disconnect sensor electrical connector
   Locate the wiring harness connector for the downstream O2 sensor. Press the release tab and carefully disconnect the electrical connector. If connector is corroded or stuck, gently wiggle while pulling to avoid breaking the connector housing.
2. 2

   Free the sensor wiring
   Trace the sensor wire from the connector to the sensor body. Release any wire clips or retainers securing the wiring to the exhaust heat shield or underbody. Ensure there is adequate slack to unthread the sensor without damaging the wire.
3. 3

   Apply penetrating oil (if needed)
   If the sensor appears corroded or vehicle has high mileage, spray penetrating oil around the base of the sensor threads where it enters the exhaust pipe. Allow 10-15 minutes for penetration. This step can prevent thread damage during removal.
4. 4

   Remove the downstream O2 sensor
   Using the O2 sensor socket and ratchet with extension, carefully loosen the sensor by turning counterclockwise. The sensor may require significant initial force to break free. Once loose, unthread completely by hand while guiding the wire through any clips. Remove the sensor from the exhaust pipe.
   ⚠If sensor is extremely difficult to remove and threads begin to bind, stop and apply more penetrating oil. Forcing a seized sensor can damage exhaust pipe threads.
5. 5

   Inspect and clean threads
   Inspect the threads in the exhaust pipe for damage or excessive carbon buildup. Use a wire brush to clean the threads in the exhaust bung. Remove any carbon deposits or debris that could prevent proper seating of the new sensor.
6. 6

   Prepare new sensor
   Remove the new oxygen sensor from packaging. Apply a thin coat of high-temperature anti-seize compound to the threads only. Do not allow anti-seize to contact the sensor tip, protective sleeve, or electrical connector. Ensure the sensor gasket or washer (if equipped) is properly positioned.
7. 7

   Install new downstream O2 sensor
   Thread the new sensor into the exhaust pipe by hand, feeding the wire through clips as needed. Turn clockwise until hand-tight, ensuring the sensor threads in smoothly without cross-threading. Once hand-tight, use the O2 sensor socket and torque wrench to tighten to specification.
   Torque spec

   O2 Sensor45 Nm (33 lb-ft)
8. 8

   Route and secure wiring
   Route the sensor wiring along its original path, ensuring it is away from hot exhaust components and moving parts. Secure the wire to all original clips and retainers. Verify there is no tension on the wire and adequate clearance from the exhaust pipe and drive axle.
9. 9

   Reconnect electrical connector
   Reconnect the electrical connector to the new O2 sensor. Press firmly until you hear or feel the locking tab engage. Gently tug on the connector to verify it is fully seated and locked in place.

Reassembly

1. Lower vehicle from jack stands using the floor jack
2. Remove jack stands and lower vehicle completely to the ground
3. Remove wheel chocks

Verification

• Start the engine and allow it to reach operating temperature while monitoring for exhaust leaks at the sensor location
• Verify no check engine light (MIL) is illuminated after 2-3 drive cycles
• Use an OBD-II scanner to verify the downstream O2 sensor is reading properly (typically 0.6-0.8V at steady cruise)
• Confirm the sensor wiring is not contacting hot exhaust components or moving parts
• Check that the electrical connector is fully seated and shows no signs of heat damage

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