Bosch 13740 Oxygen Sensor - Downstream or Upstream

Bosch Actual OE Oxygen Sensor 13740

Bosch 13740 is a specific-fit narrow-band heated oxygen sensor for select Volkswagen and Audi applications. It provides direct air-fuel-ratio feedback to the ECU for stable closed-loop control, accurate lambda monitoring, and lower emissions during normal driving.

Key Features

• Specific-fit Bosch Actual OE Oxygen Sensor for direct replacement use
• Narrow-band heated O2 sensor with 4-wire configuration
• Threaded mounting with 18 mm thread diameter and 22 mm hex size
• Oblong male connector with blade terminals
• Wiring harness included; harness length 42.4 in and overall length 46.1 in
• Metal housing built for high-temperature and vibration exposure
• Interchange reference: 021906265AG

Product Details

This Bosch oxygen sensor uses a switching-type narrow-band design to report exhaust oxygen content to the engine control unit. Bosch developed this OE-style sensor line from its long history in oxygen sensing, including early thimble designs and later planar narrowband technology that improved warm-up response, lambda accuracy, and closed-loop operation. Bosch 13740 is built with a heated ceramic sensing element and controlled heater strategy to support consistent signal output across changing exhaust temperatures.

For drivers searching for a Bosch 13740 oxygen sensor for Volkswagen Jetta downstream applications or an Audi A4 upstream oxygen sensor replacement, this part matches the listed chassis-specific fitments and OE-style connector layout. It also serves as a direct replacement for select Audi A4 Quattro, Volkswagen Golf, and Volkswagen Passat applications listed below.

This part cross-references 021906265AG for the same application.

What It Helps Address

• Check engine light caused by oxygen sensor signal faults
• Rich or lean fuel trim conditions from inaccurate exhaust feedback
• Slow closed-loop response after warm-up
• Emissions test failures related to sensor performance
• Rough idle or drivability issues tied to air-fuel control

Installation Notes

Compatible With 1995-1999 Volkswagen Passat, downstream; 1996-1999 Volkswagen Jetta, downstream; 1996-1998 Volkswagen Golf, downstream; 1997-1998 Audi A4 Quattro, upstream; and 1997-1998 Audi A4, upstream, with the chassis notes listed in the fitment data. Verify connector shape, thread size, and sensor position before installation. Use the correct oxygen sensor socket for the 22 mm hex and confirm the harness routing keeps the lead away from exhaust heat and moving components.

• Fits 1995 Volkswagen Passat, downstream
• Fits 1996-1997 Volkswagen Passat, downstream
• Fits 1996-1998 Volkswagen Golf, downstream
• Fits 1996-1999 Volkswagen Jetta, downstream
• Fits 1997-1998 Audi A4, upstream
• Fits 1997-1998 Audi A4 Quattro, upstream
• Fits 1998 Audi A4, upstream

Quality Assurance

Bosch supplies this Actual OE Oxygen Sensor line using OE-proven engineering and materials developed through more than five decades of oxygen sensor experience. The design emphasizes accurate signal control, durable heater performance, and reliable operation under thermal and vibration load.