Delphi ES20100 Oxygen Sensor - Rear

Brand Delphi ES20100
Position Rear
Sensor Type Heated
Wire Quantity 4
Connector Shape Square
Thread Size 18 x 1.5 mm
Overall Length 445.0
Package Contents Oxygen sensor, instruction sheet
Fits Mazda and Subaru · 11 vehicles

OE heritage. Built with a century of original-equipment experience.

Heated sensor. Helps the sensor reach operating temperature quickly.

Square connector. Simplifies a clean, secure electrical connection.

Cross-references Bosch 15265, Bosch 15638 and DENSO Auto Parts 234-4043 for the same application. See all 22.

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Delphi ES20100 Rear Oxygen Sensor

The Delphi ES20100 is a heated rear oxygen sensor built for precise exhaust monitoring on select Mazda 626 and Subaru applications. It combines Delphi’s OE heritage with the specifications needed for reliable replacement in emissions control service.

Key Features

  • Heated oxygen sensor for faster operating temperature and stable signal output
  • 4-wire design with a square connector shape
  • 18 x 1.5 mm thread size for direct-fit installation on listed applications
  • Overall length: 445.0
  • Includes oxygen sensor and instruction sheet
  • Rear position sensor for emissions system service

Detailed Description

Delphi ES20100 is an OE-style rear oxygen sensor engineered for vehicles that require accurate exhaust feedback after the catalytic converter. Delphi draws on more than a century of OE experience and supplier knowledge used by major automakers, bringing that background into this aftermarket replacement. This part cross-references Bosch 15265 and DENSO Auto Parts 234-4043 for the same application. It is a strong match for rear sensor service on 2001-2002 Mazda 626, 2000-2001 Subaru Impreza, 2000-2001 Subaru Legacy, and 2000-2001 Subaru Outback, including California-emissions listings where noted.

What It Helps Address

  • Check engine light related to rear oxygen sensor performance
  • Incorrect exhaust oxygen readings after the catalytic converter
  • Emissions test failures tied to sensor response or signal quality
  • Rough fuel control caused by a worn or slow-reacting sensor
  • Diagnostic trouble codes associated with rear O2 sensor circuits

Installation Notes and Tips

Verify the rear sensor location, connector shape, wire count, and thread size before installation. Confirm the vehicle’s emissions configuration, especially on California-emissions applications, and compare the original sensor length and connector style to the Delphi ES20100. For best results, inspect the harness routing and exhaust threads before fitting the new sensor.

Quality Assurance

Delphi builds this replacement using OE-focused engineering informed by its long history as a supplier to major automakers. The ES20100 is intended to meet the fitment and functional requirements of the listed Mazda and Subaru rear oxygen sensor applications.

This part fits 11 vehicles
Always verify fitment with your vehicle's VIN if unsure. Submodel & trim restrictions may apply.
YearMakeModelTransmissionPositionNotes
2002Mazda626Rear
2001Mazda626Rear
2001SubaruImprezaRear
2001SubaruLegacyManualRear
2001SubaruOutbackManualRear
2000Mazda626Rearwith California Emission System
2000SubaruImprezaRear
2000SubaruLegacyManualRear
2000SubaruOutbackManualRear
1999SubaruImprezaRearwith California Emission System
1999SubaruLegacyRearwith California Emission System
Directly replaces or cross-references 22 part numbers
Cross-reference numbers are provided for identification purposes only. Always confirm fitment before ordering.
Bosch — 15265Bosch — 15638DENSO Auto Parts — 234-4043DENSO Auto Parts — 234-4132DENSO Auto Parts — 234-4736Gates — 22104Gates — 24576Walker Products — 250-24290138-74422690 AA38A22690 AA3802131280F51K-18-861AFS1K-18-861FS1K-18-861AFS1K-18-861BOS1789REA1620SG1035SU4680SU4681SU5253