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5-pin OEM-style connector close-up on Kooks CAS-109677-8 shielded harness
Kooks CAS-109677-8 O2 extension installed on 2020 Ford Mustang GT header setup
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Kooks 18+ Ford Mustang 8in. Front O2 Extension Harness

Kooks Headers
KSHCAS-109677-8
Oxygen Sensors
20+ Units In Stock - Ships Next Business Day
$ 37.67 $ 33.90
$ 33.90

Performance Engineered in the USA: Proven Gains for Street and Track Builds

The Kooks CAS-109677-8 8-inch front oxygen sensor extension harness resolves the common issue of insufficient wiring length during header installations on 2018 and 2024 Ford Mustang GT models with the 5.0L Coyote V8, providing a plug-and-play 5-pin connection that repositions the upstream O2 sensor precisely for accurate air-fuel monitoring and ECU calibration without triggering check engine lights or lean/rich codes.

Precision-engineered from high-temperature shielded wiring with OEM-style connectors, this extension maintains signal integrity under extreme exhaust heat exceeding 1,200°F and vibration from high-RPM operation, ensuring reliable data transmission to the PCM for optimal performance mapping during dyno tunes or track sessions. The 8-inch length offers the exact reach needed for Kooks long-tube headers without excess slack that could cause chafing or shorts.

For Mustang GT owners upgrading to aftermarket headers who need a simple, reliable O2 relocation solution, the CAS-109677-8 harness delivers the essential wiring bridge for seamless installation and flawless engine management.

Key Features

  • 8-inch length for precise front O2 sensor relocation
  • 5-pin OEM-style connectors for plug-and-play fitment
  • High-temperature shielded wiring rated over 1,200°F
  • Vibration-resistant construction for track durability
  • Maintains accurate air-fuel ratio readings and ECU function
  • Direct replacement for lost or damaged extensions in header kits

Product Notes

  • Front upstream sensor extension only rear requires separate harness
  • Designed specifically for Kooks header installations on 2018+ Mustang GT
  • Inspect connections regularly to prevent heat damage

California Proposition 65: Contains chemicals known to the State of California to cause cancer or reproductive harm.

Warranty: Limited lifetime against manufacturing defects to original purchaser.

Installation Notes

  • Locate factory O2 harness and unplug sensor connector
  • Route extension harness to new sensor location avoiding exhaust heat
  • Plug into OEM harness and sensor hand-tight secure with zip ties
  • Clear any codes and perform drive cycle for ECU relearn

This Part Fits

Year Make Model Submodel/Engine
2018 and 2024 Ford Mustang GT 5.0L Coyote V8 (4V)

Note: Front upstream O2 extension for Kooks header kits. Use with 2018+ Mustang GT 5.0L only.

What's Included in the Purchase

  • (1) 8-Inch 5-Pin Oxygen Sensor Extension Harness
  • Part Number: Kooks CAS-109677-8

Why Choose Kooks?

  • Over 60 years of championship-winning exhaust engineering
  • Precision wiring components tested in 1,000+ HP builds
  • Limited lifetime warranty and expert installation support

Frequently Asked Questions

  • Q: Is this for front or rear O2 sensors?
    A: Front upstream only rear requires CAS-105979 or equivalent
  • Q: Will it work with non-Kooks headers?
    A: Yes, fits any 2018+ Mustang GT header with 5-pin O2 relocation
  • Q: Does it affect tuning?
    A: No, maintains OEM signal quality for accurate ECU readings
  • Do Kooks headers require a tune after installation?
    Yes. A professional tune is strongly recommended after installing long tube headers. The significant improvement in exhaust flow changes air fuel ratios and requires ECM recalibration to achieve optimal power output and safe operation.
  • Will these headers void my factory powertrain warranty?
    Under the Magnuson-Moss Warranty Act, a manufacturer cannot void your vehicle warranty simply because you installed an aftermarket part unless they prove the component directly caused the failure. Consult your dealer for specifics on your situation.
  • Q: Do these Kooks headers require a tune after installation?
    A: Yes. A professional tune is strongly recommended after installing long tube headers. The significant improvement in exhaust flow changes air fuel ratios and requires ECM recalibration to achieve optimal power output and safe operation.
  • Q: Will Kooks headers void my factory powertrain warranty?
    A: Under the Magnuson-Moss Warranty Act, a manufacturer cannot void your vehicle warranty simply because you installed an aftermarket part unless they prove the component directly caused the failure in question. Consult your dealer for specifics.
  • Q: What warranty does Kooks provide?
    A: Kooks products are backed by a limited lifetime warranty to the original purchaser against defects in materials and workmanship. Racing and competition use applications may have specific warranty exclusions. Contact Kooks Performance directly for warranty details.

Shipping & Handling

  • Method: UPS or Fed Ex Ground.
  • Availability: Typically ships same day or next if in stock.
  • Packaging: Anti-static bag in protective box.

Request For Information

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