exhaust

O2 Sensor - Downstream

for 2021 Toyota RAV4 2.5L I4 · AWD

Difficulty

Easy

Time

30 min

Tools

Steps

This procedure covers the removal and replacement of the downstream oxygen sensor (sensor 2) located after the catalytic converter on the 2019-2024 Toyota RAV4 2.5L I4 FWD.

Warnings

⚠️Allow exhaust system to cool completely before starting work. Exhaust components can cause severe burns for up to 1 hour after engine shutdown.

⚠The oxygen sensor is fragile and can be damaged if dropped or impacted. Handle carefully to avoid damage to the sensing element.

⚠Do not apply anti-seize to the sensor tip or sensing element. Apply only to threads.

ℹ️The downstream O2 sensor is located after the catalytic converter, approximately under the center of the vehicle.

Tools required

22mm oxygen sensor socket or 7/8" open-end wrenchEssential

3/8" drive ratchet and extensionEssential

Wire brush

Anti-seize compoundEssential

Jack and jack standsEssential

Wheel chocksEssential

Penetrating oil

Torque wrench (20-50 Nm range)Essential

Parts

Downstream oxygen sensor (Bank 1 Sensor 2) × 1 — Use OEM specification - Toyota part 89465-42100 or equivalent

Preparation

Ensure engine and exhaust system are completely cold
Park vehicle on level ground and engage parking brake
Place wheel chocks behind rear wheels
Raise front of vehicle and support securely on jack stands at manufacturer-specified lift points
Locate the downstream oxygen sensor underneath the vehicle, positioned after the catalytic converter in the exhaust pipe

Procedure

1
Disconnect oxygen sensor electrical connector
Trace the oxygen sensor wiring harness from the sensor to the electrical connector. Press the release tab and carefully disconnect the connector. If the connector is corroded or stuck, gently wiggle while pulling to separate. The connector is typically secured with a clip on the chassis or heat shield.
2
Free the sensor wiring from clips
Follow the sensor wiring and release it from any retaining clips or brackets along the exhaust or chassis. Note the routing for proper reinstallation of the new sensor.
3
Apply penetrating oil if needed
If the sensor has not been replaced recently, spray penetrating oil around the sensor threads where it enters the exhaust pipe. Allow 10-15 minutes for penetration. This step can prevent thread damage during removal.
⚠Keep penetrating oil away from the sensor tip if reusing the sensor. Contamination will cause sensor failure.
4
Remove the downstream oxygen sensor
Using a 22mm oxygen sensor socket or 7/8" open-end wrench, rotate the sensor counterclockwise to remove. The sensor socket has a slot to accommodate the wiring. Apply steady pressure; if the sensor is seized, do not force it. Instead, heat the area around the bung with a propane torch briefly to expand the metal, then retry removal. Remove the sensor completely from the exhaust pipe.
⚠Excessive force can strip threads in the exhaust pipe, requiring costly pipe replacement. Work carefully if sensor is resistant.
5
Clean the oxygen sensor bung threads
Use a wire brush to clean the threads in the exhaust pipe where the sensor mounts. Remove any carbon deposits, rust, or old anti-seize compound. Ensure threads are clean and undamaged.
6
Prepare the new oxygen sensor
Remove the new sensor from packaging carefully. Apply a thin coat of anti-seize compound to the threads only, being extremely careful not to get any on the sensor tip or perforated protective sleeve. The sensor tip must remain completely clean for proper operation.
Torque spec
O2 Sensor45 Nm (33 lb-ft)
7
Install the new oxygen sensor
Thread the new sensor into the exhaust pipe by hand, ensuring it starts straight and threads smoothly. Hand-tighten until resistance is felt. Using the oxygen sensor socket and torque wrench, tighten to 45.0 Nm (33.0 lb-ft). Do not overtighten as this can damage the sensor or exhaust pipe threads.
Torque spec
O2 Sensor45 Nm (33 lb-ft)
8
Route and secure sensor wiring
Route the new sensor wiring following the same path as the original sensor. Secure the wiring in all original clips and brackets. Ensure the wiring has adequate clearance from hot exhaust components and moving parts. The wiring should have no tension or sharp bends.
9
Connect the electrical connector
Reconnect the oxygen sensor electrical connector, ensuring it clicks firmly into place. Verify the connector lock tab is fully engaged. Ensure the connection is clean and free of moisture.

Reassembly

Double-check that the oxygen sensor electrical connector is fully seated and locked
Verify all wiring is secured and clear of exhaust and moving components
Lower vehicle from jack stands safely

Verification

Start the engine and verify no exhaust leaks are present at the oxygen sensor location
Allow the engine to reach operating temperature and verify the check engine light does not illuminate
Using an OBD-II scanner, monitor oxygen sensor readiness status and verify Bank 1 Sensor 2 is reading properly (should show voltage fluctuation between 0.1-0.9V once warmed up)
Perform a test drive and verify no diagnostic trouble codes set related to the downstream oxygen sensor (P0140, P0141, P0420, etc.)
Re-inspect the sensor area after test drive to confirm no exhaust leaks have developed