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NTKPart #: 21508
NTK 21508 Oxygen Sensor - Downstream or Upstream
⚙️ 38 vehicles fit this part
Select your vehicle to confirm fitment
Verify this part fits before purchasing — free returns if it doesn't
$100.91Free Shipping
🚚Free ShippingNo Cost to Continental U.S.
🔄Free Returns*Wrong fit? No cost
🛡️60-Day ReturnsMoney back guarantee
*Free return shipping only qualifies if our fitment verification tool is used.
🔥
✅ In Stock · Ready To Ship
Most orders ship same-day if ordered before 1pm CST.
✅OE Direct Replacement — Bolt-on fit, no modifications needed
📦Direct Fit Oxygen Sensor, Upstream and Downstream
🚗Fitment: Chevrolet, Geo, Pontiac, and Suzuki, Esteem, Sidekick, Sunrunner, Tracker, and X-90
🔄Easy Returns — Return within 60 days for a full refund
🚚Fast Shipping — Most orders ship same business day before 1pm CST
Not what you need? Click here for all Oxygen Sensor options
NTK 21508 Oxygen Sensor - Downstream or Upstream
| Brand | NTK |
| Part Number | 21508 |
| Position | Direct Fit Oxygen Sensor, Upstream and Downstream |
| Wiring Harness Length | 20.5000 |
| Sensor Type | Heated |
| Universal Or Specific Fit | Specific |
| Wire Quantity | 4 |
| Thread Diameter | 18.000 |
| Mounting Type | Threaded |
This part fits 38 vehicles. Search below:
| Year | Make | Model | Body Type | Liters | Cylinders | Position | Notes |
|---|---|---|---|---|---|---|---|
| 2002 | Suzuki | Esteem | Sedan | 1.8L | L4 | Upstream | OE design oxygen sensor fits Bank 1 Sensor 1 for air/fuel ratio.; Direct Fit Oxygen Sensor |
| 2002 | Suzuki | Esteem | Sedan | 1.8L | L4 | Downstream | Downstream oxygen sensor with original equipment equivalent design; Direct Fit Oxygen Sensor |
| 2001 | Suzuki | Esteem | Sedan | 1.8L | L4 | Upstream | OE design oxygen sensor fits Bank 1 Sensor 1 for air/fuel ratio.; Direct Fit Oxygen Sensor |
| 2001 | Suzuki | Esteem | Sedan | 1.8L | L4 | Downstream | Downstream oxygen sensor with original equipment equivalent design; Direct Fit Oxygen Sensor |
| 2000 | Suzuki | Esteem | Sedan | 1.8L | L4 | Upstream | OE design oxygen sensor fits Bank 1 Sensor 1 for air/fuel ratio.; Direct Fit Oxygen Sensor |
| 2000 | Suzuki | Esteem | Sedan | 1.8L | L4 | Downstream | Downstream oxygen sensor with original equipment equivalent design; Direct Fit Oxygen Sensor |
| 2000 | Suzuki | Esteem | 1.6L | L4 | Upstream | OE design oxygen sensor fits Bank 1 Sensor 1 for air/fuel ratio.; Direct Fit Oxygen Sensor | |
| 2000 | Suzuki | Esteem | 1.6L | L4 | Downstream | Downstream oxygen sensor with original equipment equivalent design; Direct Fit Oxygen Sensor | |
| 1999 | Suzuki | Esteem | 1.8L | L4 | Upstream | OE design oxygen sensor fits Bank 1 Sensor 1 for air/fuel ratio.; Direct Fit Oxygen Sensor | |
| 1999 | Suzuki | Esteem | 1.8L | L4 | Downstream | Downstream oxygen sensor with original equipment equivalent design; Direct Fit Oxygen Sensor | |
| 1999 | Suzuki | Esteem | 1.6L | L4 | Upstream | OE design oxygen sensor fits Bank 1 Sensor 1 for air/fuel ratio.; Direct Fit Oxygen Sensor | |
| 1999 | Suzuki | Esteem | 1.6L | L4 | Downstream | Downstream oxygen sensor with original equipment equivalent design; Direct Fit Oxygen Sensor | |
| 1998 | Chevrolet | Tracker | 1.6L | L4 | Upstream | OE design oxygen sensor fits Bank 1 Sensor 1 for air/fuel ratio.; Direct Fit Oxygen Sensor | |
| 1998 | Suzuki | Esteem | 1.6L | L4 | Upstream | OE design oxygen sensor fits Bank 1 Sensor 1 for air/fuel ratio.; Direct Fit Oxygen Sensor | |
| 1998 | Suzuki | Esteem | 1.6L | L4 | Downstream | Downstream oxygen sensor with original equipment equivalent design; Direct Fit Oxygen Sensor | |
| 1998 | Suzuki | Sidekick | 1.6L | L4 | Upstream | OE design oxygen sensor fits Bank 1 Sensor 1 for air/fuel ratio.; Direct Fit Oxygen Sensor | |
| 1998 | Suzuki | X-90 | 1.6L | L4 | Upstream | OE design oxygen sensor fits Bank 1 Sensor 1 for air/fuel ratio.; Direct Fit Oxygen Sensor | |
| 1997 | Geo | Tracker | 1.6L | L4 | Upstream | OE design oxygen sensor fits Bank 1 Sensor 1 for air/fuel ratio.; Direct Fit Oxygen Sensor | |
| 1997 | Pontiac | Sunrunner | 1.6L | L4 | Upstream | OE design oxygen sensor fits Bank 1 Sensor 1 for air/fuel ratio.; Direct Fit Oxygen Sensor | |
| 1997 | Suzuki | Esteem | 1.6L | L4 | Upstream | OE design oxygen sensor fits Bank 1 Sensor 1 for air/fuel ratio.; Direct Fit Oxygen Sensor | |
| 1997 | Suzuki | Esteem | 1.6L | L4 | Downstream | Downstream oxygen sensor with original equipment equivalent design; Direct Fit Oxygen Sensor | |
| 1997 | Suzuki | Sidekick | 1.6L | L4 | Upstream | OE design oxygen sensor fits Bank 1 Sensor 1 for air/fuel ratio.; Direct Fit Oxygen Sensor | |
| 1997 | Suzuki | X-90 | 1.6L | L4 | Upstream | OE design oxygen sensor fits Bank 1 Sensor 1 for air/fuel ratio.; Direct Fit Oxygen Sensor | |
| 1996 | Geo | Tracker | 1.6L | L4 | Upstream | OE design oxygen sensor fits Bank 1 Sensor 1 for air/fuel ratio.; Direct Fit Oxygen Sensor | |
| 1996 | Pontiac | Sunrunner | 1.6L | L4 | Upstream | OE design oxygen sensor fits Bank 1 Sensor 1 for air/fuel ratio.; Direct Fit Oxygen Sensor | |
| 1996 | Suzuki | Esteem | 1.6L | L4 | Upstream | OE design oxygen sensor fits Bank 1 Sensor 1 for air/fuel ratio.; Direct Fit Oxygen Sensor | |
| 1996 | Suzuki | Esteem | 1.6L | L4 | Downstream | Downstream oxygen sensor with original equipment equivalent design; Direct Fit Oxygen Sensor | |
| 1996 | Suzuki | Sidekick | 1.6L | L4 | Upstream | OE design oxygen sensor fits Bank 1 Sensor 1 for air/fuel ratio.; Direct Fit Oxygen Sensor | |
| 1996 | Suzuki | X-90 | 1.6L | L4 | Upstream | OE design oxygen sensor fits Bank 1 Sensor 1 for air/fuel ratio.; Direct Fit Oxygen Sensor | |
| 1995 | Geo | Tracker | 1.6L | L4 | Upstream | B1S1; Calif. Emissions; OE Equivalent Design; Direct Fit Oxygen Sensor | |
| 1995 | Pontiac | Sunrunner | 1.6L | L4 | Upstream | B1S1; Calif. Emissions; OE Equivalent Design; Direct Fit Oxygen Sensor | |
| 1995 | Suzuki | Esteem | 1.6L | L4 | Upstream | OE design oxygen sensor fits Bank 1 Sensor 1 for air/fuel ratio.; Direct Fit Oxygen Sensor | |
| 1995 | Suzuki | Sidekick | 1.6L | L4 | Upstream | B1S1; Calif. Emissions; OE Equivalent Design; Direct Fit Oxygen Sensor | |
| 1994 | Geo | Tracker | 1.6L | L4 | Upstream | B1S1; Calif. Emissions; OE Equivalent Design; Direct Fit Oxygen Sensor | |
| 1994 | Pontiac | Sunrunner | 1.6L | L4 | Upstream | B1S1; Calif. Emissions; OE Equivalent Design; Direct Fit Oxygen Sensor | |
| 1994 | Suzuki | Sidekick | 1.6L | L4 | Upstream | B1S1; Calif. Emissions; OE Equivalent Design; Direct Fit Oxygen Sensor | |
| 1993 | Geo | Tracker | 1.6L | L4 | Upstream | B1S1; Calif. Emissions; OE Equivalent Design; Direct Fit Oxygen Sensor | |
| 1993 | Suzuki | Sidekick | 1.6L | L4 | Upstream | B1S1; Hard Top; Calif. Emissions; OE Equivalent Design; Direct Fit Oxygen Sensor |
* Always verify fitment with your vehicle's VIN if unsure. Submodel & trim restrictions may apply.
This part directly replaces or is cross-referenced with the following part numbers:
1307315053150591821358B111821358B211821360G11213-1362213-3131213-404234-4060234-423475-182575-344675-345191177408ES20191OS5204OS615SG322
Cross-reference numbers are provided for identification purposes only. Always confirm fitment before ordering.