NTK 27004 Air / Fuel Ratio Sensor - Upstream
OE Quality 60-Day Returns
NTK
 Direct Fit 5-Wire A/F Sensor

NTK 27004 Air / Fuel Ratio Sensor - Upstream

Brand NTK 27004
Position Upstream
Wiring Harness Length 11.0
Sensor Type Heated
Thread Length 0.38
Universal Or Specific Fit Specific
Wire Quantity 5
Thread Diameter 18.000
Mounting Bracket Included No
Product line Direct Fit 5-Wire A/F Sensor
Fits Subaru · 12 vehicles

Direct fit replacement. Specific-fit sensor for straightforward installation.

Heated sensor. Helps the sensor reach operating temperature quickly.

OE-spec tested. Manufactured to meet or exceed original equipment standards.

Cross-references DENSO Auto Parts 234-5178 and 22641AA650 for the same application. See all 2.

$153.21Free shipping
In stock · usually ships same day before 1pm CST
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Order total $153.21
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Free returns within 60 days if it doesn't fit when fitment is verified.
Not what you need? See all Air / Fuel Ratio Sensor options

NTK Direct Fit Air/Fuel Ratio Sensor

NTK Part Number 27004 is a direct fit heated air/fuel ratio sensor built for specific Subaru applications. It is engineered for upstream monitoring and uses a 5-wire design with an 18 mm thread diameter and 11.0 in. wiring harness length for OE-style replacement.

The NTK Direct Fit 5-Wire A/F Sensor line focuses on exact application coverage, proper connector fit, and sensor performance aligned with original equipment requirements. For Subaru WRX and Subaru Forester upstream service, NTK 27004 provides a direct-fit solution without universal adaptation.

Key Features

  • Heated air/fuel ratio sensor for upstream exhaust placement
  • Specific-fit design for OE-style installation
  • 5-wire configuration for accurate signal communication
  • 18.000 mm thread diameter with 0.38 in. thread length
  • 11.0 in. wiring harness length
  • No mounting bracket included
  • NTK Part Number 27004 for application matching

Application Coverage

  • Fits 2021 Subaru WRX, Upstream
  • Fits 2015-2020 Subaru WRX, Upstream, Bank 1 Sensor 1 Oxygen Sensor
  • Fits 2014-2018 Subaru Forester, Upstream, Bank 1 Sensor 1 Oxygen Sensor

This part cross-references DENSO Auto Parts 234-5178 and Subaru 22641AA650 for the same application.

What It Helps Address

  • Check engine lights related to upstream air/fuel ratio sensor faults
  • Incorrect fuel trim readings from a worn sensor
  • Slow sensor response affecting drivability and emissions control
  • Failed inspection results tied to emissions monitoring issues
  • Signal instability caused by age, heat, or contamination

Installation Notes

Verify the connector, thread size, and upstream location before installation. NTK 27004 is a specific-fit sensor for Subaru WRX and Subaru Forester applications, so confirm the vehicle year and engine configuration against the listed fitment before replacing the original sensor. Use proper exhaust sensor removal tools and follow factory torque and routing procedures to protect the harness.

Quality Assurance

NTK is a major original equipment oxygen sensor supplier and manufactures sensors with ceramic technology control from raw material through finished product. Each sensor is tested during production to help ensure fit, form, function, and performance that meet or exceed OE specifications.

Related reading

This part fits 12 vehicles
Always verify fitment with your vehicle's VIN if unsure. Submodel & trim restrictions may apply.
YearMakeModelLitersCylindersPositionNotes
2021SubaruWRX2.0LH4UpstreamOE MFR: NTK; Direct Fit 5-Wire A/F Sensor
2020SubaruWRX2.0LH4UpstreamBank 1 Sensor 1 Oxygen Sensor; Direct Fit 5-Wire A/F Sensor
2019SubaruWRX2.0LH4UpstreamBank 1 Sensor 1 Oxygen Sensor; Direct Fit 5-Wire A/F Sensor
2018SubaruForester2.0LH4UpstreamBank 1 Sensor 1 Oxygen Sensor; Direct Fit 5-Wire A/F Sensor
2018SubaruWRX2.0LH4UpstreamBank 1 Sensor 1 Oxygen Sensor; Direct Fit 5-Wire A/F Sensor
2017SubaruForester2.0LH4UpstreamBank 1 Sensor 1 Oxygen Sensor; Direct Fit 5-Wire A/F Sensor
2017SubaruWRX2.0LH4UpstreamBank 1 Sensor 1 Oxygen Sensor; Direct Fit 5-Wire A/F Sensor
2016SubaruForester2.0LH4UpstreamBank 1 Sensor 1 Oxygen Sensor; Direct Fit 5-Wire A/F Sensor
2016SubaruWRX2.0LH4UpstreamBank 1 Sensor 1 Oxygen Sensor; Direct Fit 5-Wire A/F Sensor
2015SubaruForester2.0LH4UpstreamBank 1 Sensor 1 Oxygen Sensor; Direct Fit 5-Wire A/F Sensor
2015SubaruWRX2.0LH4UpstreamBank 1 Sensor 1 Oxygen Sensor; Direct Fit 5-Wire A/F Sensor
2014SubaruForester2.0LH4UpstreamBank 1 Sensor 1 Oxygen Sensor; Direct Fit 5-Wire A/F Sensor
Directly replaces or cross-references 2 part numbers
Cross-reference numbers are provided for identification purposes only. Always confirm fitment before ordering.
DENSO Auto Parts — 234-517822641AA650