Delphi ES20166 Oxygen Sensor - Front, Rear, Rear Left or Rear Right

Delphi ES20166 Oxygen Sensor Overview

The Delphi ES20166 is a heated oxygen sensor built for select Audi and Volkswagen applications that require a 4-wire, flat-connector replacement with an 18 x 1.5 mm thread. With OE heritage drawn from Delphi’s long history supplying major automakers, this sensor is built to match the demands of rear and front exhaust monitoring on covered vehicles.

Compatible With Audi A4, Audi A4 Quattro, Audi A6, Audi A6 Quattro, Audi TT, Volkswagen Golf, Volkswagen Jetta, Volkswagen Passat, and other listed applications, the ES20166 supports accurate exhaust feedback for drivability and emissions control. Part number ES20166 is also referenced by several OE and aftermarket cross numbers for the same application.

Key Features

• Heated oxygen sensor for faster operating temperature and stable signal output
• 4-wire design with flat connector shape
• 18 x 1.5 mm thread size for direct-fit exhaust mounting
• Overall length: 1530.0 mm
• Supplied with oxygen sensor and instruction sheet
• Positions listed for front, rear, rear left, and rear right applications

Detailed Description

Delphi ES20166 is an OE-style oxygen sensor engineered for specific Audi and Volkswagen exhaust layouts, including rear sensor locations on the A4, A4 Quattro, A6, A6 Quattro, TT, Golf, Jetta, Passat, and related models. The heated sensor design helps the unit reach operating temperature quickly so the engine control system can monitor exhaust oxygen content more consistently after startup. This part number, ES20166, is built around the fitment and connector requirements shown in the application data, including the 1530 mm lead length used on the listed vehicles.

This part cross-references Bosch 16978 and DENSO Auto Parts 234-4809 for the same application.

What This Sensor Helps Address

• Check engine light concerns related to oxygen sensor performance
• Incorrect air-fuel feedback from a worn or slow-responding sensor
• Emissions test failures tied to exhaust monitoring faults
• Rough idle or drivability issues caused by inaccurate sensor readings
• Replacement needs after sensor aging, contamination, or wiring wear

Installation Notes and Tips

• Verify the exact position on your vehicle before ordering; this part is listed for front, rear, rear left, and rear right locations depending on application.
• Confirm connector shape, wire count, thread size, and overall lead length against the original sensor.
• Inspect the exhaust bung and harness routing before installation to ensure proper fitment on Audi and Volkswagen models.
• Follow the included instruction sheet and use the vehicle application data for the correct mounting location.

Quality Assurance

Delphi draws on more than a century of OE experience and supplier knowledge used by major automakers. That OE background is reflected in the ES20166 oxygen sensor design, materials, and application-specific fitment for covered Audi and Volkswagen vehicles.