NTK 21023 Oxygen Sensor - Downstream

Direct Fit Downstream Oxygen Sensor

NTK Direct Fit Oxygen Sensor 21023 is a heated, threaded oxygen sensor built for specific-fit replacement on downstream applications. It is engineered with a 4-wire layout, 18 mm thread diameter, and a 12.2500-inch wiring harness length for a direct replacement on select Buick, Chevrolet, GMC, Isuzu, Pontiac, and Saab vehicles.

Key Features

• Heated oxygen sensor for downstream exhaust monitoring
• Specific fit design for direct replacement
• 4-wire configuration
• 18 mm threaded mounting type
• 12.2500-inch wiring harness length
• NTK part number 21023

Product Details

NTK is the Sensor Specialist for import and domestic applications, and this Direct Fit Oxygen Sensor line is built to streamline coverage while maintaining OE-style fit, form, and function. Part number 21023 is manufactured with NTK’s ceramic-focused process control and is extensively tested during production to meet or exceed OE specifications. It is a downstream B1S2 oxygen sensor application for vehicles such as the 2008-2009 Buick Allure, 2008-2009 Buick LaCrosse, and 2008-2009 Chevrolet Impala, along with additional coverage for the 2006 Chevrolet Colorado and 2006 GMC Canyon.

This part cross-references DENSO Auto Parts 234-4249 for the same application.

What It Helps Address

• Check engine light related to downstream oxygen sensor performance
• Incorrect air-fuel feedback from a worn heated O2 sensor
• Emissions test failures tied to sensor response issues
• Rough idle or drivability concerns caused by inaccurate exhaust readings
• Fault codes associated with B1S2 downstream sensor operation

Installation Notes and Tips

• Verify the vehicle uses the downstream B1S2 position before ordering.
• Confirm the 4-wire connector and 18 mm threaded mounting style match the original sensor.
• Inspect the exhaust bung and wiring route before installation.
• Use the vehicle’s service procedure for sensor removal and torque specification.
• Clear diagnostic trouble codes after installation and verify sensor operation.

Quality Assurance

NTK manufactures oxygen sensors with OE-level application coverage and extensive production testing for quality and reliability. The 21023 is built to meet or exceed OE specifications for the listed applications, including Buick Allure, Buick LaCrosse, and Chevrolet Impala downstream service.