This procedure covers the removal and replacement of the downstream oxygen sensor (Bank 1 Sensor 2) on a 2016-2024 Hyundai Tucson with the 2.5L I4 engine and AWD.

Warnings

Tools required

Parts

• Downstream O2 sensor (Bank 1 Sensor 2) × 1 — Use OEM specification or compatible aftermarket

Preparation

1. Ensure the exhaust system is completely cool to the touch
2. Park vehicle on level surface and engage parking brake
3. If checking for diagnostic trouble codes, connect OBD-II scanner and document codes before starting
4. Raise and support vehicle securely on jack stands at manufacturer-specified lift points
5. Locate the downstream O2 sensor - it will be positioned after the catalytic converter on the exhaust pipe

Procedure

1. 1

   Disconnect sensor electrical connector
   Trace the O2 sensor wire harness from the sensor to the electrical connector. Press the release tab and disconnect the connector. The connector may be clipped to a bracket on the underbody - release any clips securing the harness.
2. 2

   Apply penetrating oil (if needed)
   If the sensor has been in place for an extended period or shows corrosion, apply penetrating oil to the sensor threads where it meets the exhaust pipe. Allow 10-15 minutes for penetration. This step can prevent thread damage during removal.
   ⚠Keep penetrating oil away from sensor tip and connector. Only apply to external threads.
3. 3

   Remove downstream O2 sensor
   Using the O2 sensor socket and ratchet with extension, turn the sensor counterclockwise to remove. The sensor socket has a slot to clear the wire harness. If resistance is encountered, do not force - reapply penetrating oil and allow more time. Remove the sensor completely from the exhaust pipe.
   ⚠Excessive force can strip threads in the exhaust pipe bung, requiring costly repair. If sensor is seized, apply heat with a heat gun (not torch) to expand the pipe.
4. 4

   Inspect and clean threads
   Examine the threads in the exhaust pipe bung for damage or carbon buildup. Use a wire brush to clean the threads thoroughly. Check the old sensor threads for signs of damage or excessive corrosion. Inspect the sensor bung for cracks in the weld or pipe.
5. 5

   Prepare new sensor
   Remove the new O2 sensor from packaging carefully. Apply a thin coat of anti-seize compound to the threads only - do NOT get anti-seize on the sensor tip, protective sleeve, or any part of the sensing element. Apply anti-seize to approximately the first 3-4 threads.
   ⚠Anti-seize on the sensor element will cause immediate sensor failure and inaccurate readings.
6. 6

   Install new O2 sensor
   Thread the new sensor into the exhaust pipe bung by hand, ensuring the wiring harness routes properly and will not contact hot exhaust components or moving parts. Hand-tighten until resistance is felt, then use the O2 sensor socket and torque wrench to tighten to specification.
   Torque spec

   O2 Sensor45 Nm (33 lb-ft)
7. 7

   Connect electrical harness
   Route the sensor wire harness to avoid contact with exhaust components, suspension parts, or the driveshaft. Connect the electrical connector to the vehicle harness, ensuring it clicks securely into place. Secure any harness clips to mounting brackets to prevent wire chafing.
8. 8

   Lower vehicle and clear codes
   Lower the vehicle from jack stands. If diagnostic trouble codes were present, use an OBD-II scanner to clear the codes from the ECU. This allows you to verify the repair by checking if the code returns.

Reassembly

1. Ensure all harness clips are secured and wiring is not hanging loose or contacting hot/moving components
2. Verify the sensor connector is fully engaged with positive click
3. Double-check that no tools or parts were left in the work area under the vehicle

Verification

• Start the engine and allow it to reach normal operating temperature - the O2 sensor requires heat to function
• Check for exhaust leaks around the sensor installation point - there should be no hissing or visible smoke
• Use an OBD-II scanner to monitor live data for the downstream O2 sensor - it should show voltage fluctuations between approximately 0.1-0.9 volts once warmed up
• Take the vehicle for a test drive of at least 10-15 minutes to allow the ECU to complete monitor readiness tests
• Re-scan for diagnostic trouble codes - if installation was successful, no O2 sensor codes should return
• Verify the sensor wire harness has not shifted and is clear of exhaust and moving components

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