NTK 25603 Oxygen Sensor - Downstream

Direct Fit Oxygen Sensor Overview

The NTK 25603 is a direct fit heated oxygen sensor built for specific applications and threaded mounting. It is engineered with a 4-wire design and a 38.2500 wiring harness length for a precise replacement on select Volvo emissions systems.

Fits 2000-2004 Volvo S40, downstream. Fits 2000-2004 Volvo V40, downstream.

Key Features

• Heated oxygen sensor for faster operating response.
• Specific-fit design for direct replacement applications.
• 4-wire configuration with threaded mounting.
• 38.2500 wiring harness length.
• Original equipment equivalent design for downstream use.

Detailed Description

NTK 25603 is part of the Direct Fit Oxygen Sensor line, which focuses on application-specific replacement parts with OE-style fit, form, and function. As an oxygen sensor from NTK, The Sensor Specialist, it reflects the brand’s OE-focused engineering and manufacturing approach. This part cross-references Bosch 16292 and Delphi ES20167 for the same application.

For Volvo S40 and Volvo V40 emissions service, this downstream oxygen sensor helps restore accurate exhaust monitoring in the vehicle’s control system. The heated design supports quicker sensor operation, while the threaded mounting style and specific-fit construction simplify matching the original configuration. The NTK 25603 is also referenced by part number 25603 for catalog and search use.

What It Is Used For

• Replacing a worn downstream oxygen sensor.
• Restoring exhaust gas feedback to the engine management system.
• Addressing sensor-related fault codes tied to emissions monitoring.
• Correcting slow sensor response from aging heated sensor elements.
• Maintaining proper emissions system operation on Volvo S40 and Volvo V40 applications.

Installation Notes and Tips

Verify the downstream location and connector match before installation. Confirm thread diameter and harness length against the original sensor to ensure proper routing and fitment. Use the vehicle’s service procedure for removal and installation on the exhaust stream.

Quality Assurance

NTK states that these oxygen sensors are extensively tested during manufacturing to meet or exceed OE specifications. The brand also positions this line as an OE-focused replacement solution backed by original equipment sensor manufacturing expertise.