Denso 234-4120 Oxygen Sensor - Downstream

Denso OE Style Oxygen Sensor 234-4120

Denso 234-4120 is an OE Style heated oxygen sensor built for exact replacement and first-time fit. It is designed for downstream use on select Audi applications, including Audi Q5, S5, SQ5, S4, A6 Quattro, A7 Quattro, A8 Quattro, A5 Quattro, and A4 Quattro.

The Denso OE Style line focuses on factory-style fitment and consistent sensor response. This oxygen sensor uses a threaded mounting design, a male connector, 4 wires, and a 19.69 in. wiring harness length for a direct replacement on the listed vehicles.

Key Features

• Heated oxygen sensor for downstream placement
• Specific fit design for the listed Audi applications
• Threaded mounting type with 0.708 in. thread diameter
• 4-wire configuration with male connector
• 19.69 in. wiring harness length
• OE Style replacement built to match factory fit and function

Product Details

Denso 234-4120 is engineered to meet strict OE standards and is precision built as a direct replacement for the original sensor. The OE Style design helps maintain proper exhaust feedback on the supported Audi models, including downstream positions on the 2009-2017 Audi Q5, 2010-2017 Audi S5, 2014-2017 Audi SQ5, 2010-2016 Audi S4, 2012-2015 Audi A6 Quattro, 2012-2015 Audi A7 Quattro, 2013-2014 Audi A8 Quattro, 2008-2010 Audi A5 Quattro, and 2009 Audi A4 Quattro. This part cross-references Bosch 18026 and NTK 25197 for the same application.

Denso’s sensor design includes an aluminum oxide trap layer that helps protect the ceramic element from silicone and lead contamination, supporting stable engine performance and fuel efficiency over time. If you are replacing a downstream oxygen sensor on an Audi Q5 or Audi S5, Denso 234-4120 provides the OE-style fit and connector layout needed for a clean replacement.

Common Issues This Part May Address

• Check engine light related to oxygen sensor performance
• Slow or inaccurate downstream sensor response
• Fault codes tied to exhaust mixture monitoring
• Reduced fuel economy caused by a failing sensor
• Rough engine operation from incorrect exhaust feedback

Installation Notes and Tips

Confirm the vehicle’s year, model, and downstream sensor position before ordering. Match the connector style, wire count, and threaded mounting dimensions to the original part for proper installation. Inspect the exhaust bung and wiring routing before replacement, and verify that the harness length is sufficient for the factory routing path.

Quality Assurance

Denso manufactures and tests this oxygen sensor to strict OE standards for consistent fit and performance. The OE Style construction is intended to deliver the correct part and fit for the listed Audi applications.