NTK 21577 Oxygen Sensor - Upstream

Direct-Fit Oxygen Sensor

NTK 21577 is a specific-fit heated oxygen sensor built for direct replacement applications. It uses a threaded mounting design, a 4-wire configuration, and a 20.75-inch harness for a clean OE-style installation.

Key Features

• Specific-fit oxygen sensor for direct replacement service
• Heated sensor design for faster operating response
• 4-wire construction for signal and heater circuit operation
• Threaded mounting type for secure installation
• 20.75-inch wiring harness length
• 18 mm thread diameter

Detailed Description

NTK 21577 is a direct fit oxygen sensor engineered for upstream air/fuel ratio monitoring. It is listed for 2021 Buick Encore and 2021 Chevrolet Trax, along with 2011-2020 Chevrolet Cruze, Chevrolet Sonic, Chevrolet Volt, Chevrolet Trax, Buick Encore, and Cadillac ELR applications. This part cross-references Bosch 16734 and DENSO Auto Parts 234-4529 for the same application. As part of the NTK Direct Fit Oxygen Sensor line, it reflects NTK's OE-focused approach to sensor coverage and application-specific fitment. The NTK 21577 supports accurate exhaust feedback in vehicles such as the Chevrolet Cruze and Buick Encore when the original sensor needs replacement.

Common Issues Addressed

• Fault codes related to oxygen sensor performance
• Delayed or unstable air/fuel ratio feedback
• Rough idle or drivability concerns tied to upstream sensor output
• Emissions test failures caused by a worn sensor
• Replacement needs for a damaged threaded sensor assembly

Installation Notes

Verify the upstream position and bank/sensor application before ordering. Confirm the 18 mm thread diameter, 4-wire layout, and harness length against the original part. Use the vehicle's service procedure for removal and installation to ensure proper sensor seating and connector routing.

Quality Assurance

NTK tests oxygen sensors during manufacturing to meet or exceed OE specifications. The brand is part of the NGK family and is recognized as a major OE oxygen sensor supplier.