O2 Sensors - All

This procedure covers the removal and replacement of both oxygen sensors (upstream and downstream) on the 2018-2024 Honda Accord 1.5L turbocharged engine.

Warnings

Tools required

Parts

• Upstream oxygen sensor (Air/Fuel sensor) × 1 — Use OEM specification
• Downstream oxygen sensor × 1 — Use OEM specification

Preparation

1. Ensure engine and exhaust system are completely cool to the touch
2. Disconnect negative battery terminal and wait 3 minutes for system discharge
3. Raise vehicle on jack stands and ensure it is secure on level ground
4. Locate both oxygen sensors: upstream sensor is in the exhaust manifold before the turbocharger, downstream sensor is after the catalytic converter
5. If sensors are corroded, spray threads with penetrating oil and allow 15 minutes soak time

Procedure

1. 1

   Access upstream oxygen sensor
   From the engine bay, locate the upstream Air/Fuel Ratio sensor on the exhaust manifold near the turbocharger. It will have a gray or white electrical connector. You may need to remove the engine cover by pulling upward on the oil cap side first, then lifting off.
2. 2

   Disconnect upstream sensor electrical connector
   Press the locking tab on the upstream sensor connector and pull straight apart. The connector may be clipped to a bracket - release any clips or routing guides. Note the wire routing for reinstallation.
3. 3

   Remove upstream oxygen sensor
   Using the oxygen sensor socket and ratchet with extension, carefully loosen the upstream sensor by turning counterclockwise. The sensor is located in a tight area near the turbo. If resistance is high, do not force - reapply penetrating oil and wait. Remove the sensor completely and inspect the threads in the manifold.
4. 4

   Access downstream oxygen sensor
   From underneath the vehicle, locate the downstream oxygen sensor mounted in the exhaust pipe after the catalytic converter, approximately mid-vehicle. The sensor will have a black electrical connector.
5. 5

   Disconnect downstream sensor electrical connector
   Press the locking tab on the downstream sensor connector and separate. The connector may be secured to the chassis or heat shield with a clip - release if present. Note wire routing.
6. 6

   Remove downstream oxygen sensor
   Using the oxygen sensor socket and ratchet, loosen the downstream sensor by turning counterclockwise. Remove the sensor completely. Inspect the threads in the exhaust pipe for damage or excessive carbon buildup.
7. 7

   Clean sensor bungs
   Use a wire brush to clean the threads in both sensor mounting locations. Remove any carbon deposits or corrosion from the threads. Ensure threads are clean and smooth to prevent cross-threading during installation.
8. 8

   Prepare new upstream sensor
   Apply a thin coat of nickel-based anti-seize compound to the threads of the new upstream Air/Fuel sensor only. Keep anti-seize away from the sensor tip by at least 3 threads. Do not over-apply as excess can contaminate the sensor element.
   Torque spec

   O2 Sensor45 Nm (33 lb-ft)
9. 9

   Install upstream oxygen sensor
   Carefully start the upstream sensor by hand, ensuring it threads smoothly without resistance. Thread in at least 3-4 full turns by hand to confirm proper threading. Once confirmed, use the oxygen sensor socket and torque wrench to tighten to specification.
   Torque spec

   O2 Sensor45 Nm (33 lb-ft)
10. 10

    Prepare new downstream sensor
    Apply a thin coat of nickel-based anti-seize compound to the threads of the new downstream oxygen sensor only. Keep anti-seize away from the sensor tip by at least 3 threads.
    Torque spec

    O2 Sensor45 Nm (33 lb-ft)
11. 11

    Install downstream oxygen sensor
    Carefully start the downstream sensor by hand, ensuring smooth threading. Thread in at least 3-4 full turns by hand before using tools. Use the oxygen sensor socket and torque wrench to tighten to specification.
    Torque spec

    O2 Sensor45 Nm (33 lb-ft)
12. 12

    Reconnect electrical connectors
    Route the upstream sensor wire following the original path, ensuring it does not contact hot exhaust components or moving parts. Connect the electrical connector until it clicks. Secure any wire clips or brackets. Repeat for the downstream sensor, ensuring proper routing away from heat and moving components.
13. 13

    Reconnect battery and clear codes
    Reconnect the negative battery terminal. Start the vehicle and allow it to idle. The check engine light may illuminate briefly then extinguish. If a code reader is available, clear any stored O2 sensor codes to establish a fresh baseline.

Reassembly

1. Reinstall engine cover if removed by aligning grommets and pressing down firmly
2. Lower vehicle from jack stands
3. Verify all electrical connectors are fully seated and locked
4. Ensure no tools or parts were left in the engine bay or under the vehicle

Verification

• Start the engine and verify no exhaust leaks are present at either sensor location (listen for hissing sounds)
• Check that the check engine light remains off after 30 seconds of idling
• Allow vehicle to reach operating temperature and verify smooth idle with no warning lights
• Test drive for 10-15 minutes through varied conditions to allow the PCM to confirm sensor operation
• If available, use a scan tool to verify both sensors are reading and switching properly (upstream: 0-5V varying, downstream: slower switching around 0.4-0.6V)

More procedures for this vehicle