{"product_id":"ntk-25540-oxygen-sensor-upstream","title":"NTK 25540 Oxygen Sensor - Upstream","description":"\u003ch2\u003eDirect Fit Oxygen Sensor for BMW\u003c\/h2\u003e\u003cp\u003eNTK 25540 is a direct fit heated oxygen sensor built for specific BMW applications. It uses a threaded mounting design and a 4-wire configuration to match the original sensor layout for accurate air-fuel feedback.\u003c\/p\u003e\u003ch2\u003eKey Features\u003c\/h2\u003e\u003cul\u003e\n\u003cli\u003eDirect fit design for specific applications\u003c\/li\u003e\n\u003cli\u003eHeated oxygen sensor for faster operating response\u003c\/li\u003e\n\u003cli\u003e4-wire configuration\u003c\/li\u003e\n\u003cli\u003eThreaded mounting type with 18 mm thread diameter\u003c\/li\u003e\n\u003cli\u003e20.5 in. harness length\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch2\u003eDetailed Description\u003c\/h2\u003e\u003cp\u003eNTK 25540 is part of the Direct Fit Oxygen Sensor line, which focuses on application-specific replacement sensors with OE-style fit, form, and function. NTK draws on its background as a major oxygen sensor manufacturer and uses controlled ceramic technology from raw material through finished production. This sensor is engineered for upstream use on BMW 325i, BMW 325is, and BMW 325iX applications listed for 1987-1988, including Bank 1 Sensor 1 coverage noted in the fitment data. The part number 25540 is also referenced across multiple aftermarket listings for the same application.\u003c\/p\u003e\u003ch2\u003eWhat It Helps Address\u003c\/h2\u003e\u003cul\u003e\n\u003cli\u003eFaulty oxygen sensor readings\u003c\/li\u003e\n\u003cli\u003eCheck engine light concerns related to mixture control\u003c\/li\u003e\n\u003cli\u003eSlow sensor response during closed-loop operation\u003c\/li\u003e\n\u003cli\u003eIncorrect air-fuel ratio feedback\u003c\/li\u003e\n\u003cli\u003eEmissions performance issues tied to sensor wear\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch2\u003eInstallation Notes and Tips\u003c\/h2\u003e\u003cp\u003eConfirm the upstream location, thread size, and harness length before installation. This sensor uses a threaded mount and a specific 4-wire layout, so connector and routing verification is important before replacement. For BMW 325i, BMW 325is, and BMW 325iX applications, match the fitment notes carefully, especially the 9\/87 cutoff listed for 1988 models.\u003c\/p\u003e\u003ch2\u003eQuality Assurance\u003c\/h2\u003e\u003cp\u003eNTK states that these oxygen sensors are extensively tested during manufacturing to meet or exceed OE specifications. The brand is part of the NGK family and is recognized for original equipment oxygen sensor production and application coverage.\u003c\/p\u003e","brand":"NTK","offers":[{"title":"Default Title","offer_id":53731437576373,"sku":"BFPZ-25540","price":89.63,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0628\/1442\/1173\/files\/NO_25540_Fro.jpg?v=1794296249","url":"https:\/\/www.partcatalog.com\/products\/ntk-25540-oxygen-sensor-upstream","provider":"PartCatalog","version":"1.0","type":"link"}