What size thread is a Tacoma O2 sensor?
The oxygen sensors in most Toyota Tacomas use an M18 x 1.5 thread—roughly 18 mm in diameter with a 1.5 mm pitch. This size covers both upstream and downstream sensors for the majority of model years. If you’re replacing a sensor, that is the standard to expect, though some aftermarket or older installations may differ.
In this article, we’ll explain the typical thread size, how to verify the exact size for your truck’s year and engine, and tips for buying a replacement sensor.
Thread size basics for Toyota Tacoma oxygen sensors
Most Tacomas follow a single standard for O2-sensor threads, simplifying replacements. The information below reflects what you’re most likely to encounter when working on a 2005–2024 Tacoma or similar generations.
- Upstream (pre-cat) O2 sensor: M18 x 1.5 thread
- Downstream (post-cat) O2 sensor: M18 x 1.5 thread
- Many aftermarket/universal sensors: commonly M18 x 1.5, but some options are offered in 1/2-20 UNF. Always check the product specifications to confirm the thread size.
In practice, the vast majority of Tacoma O2 sensors use the M18 x 1.5 thread. If a replacement part lists a different size, verify against your own sensor or consult the dealer for the exact specification for your VIN and engine code.
How to confirm your Tacoma’s O2 sensor thread size
To ensure you’re buying the right sensor, use one of these verification methods before purchasing or installing a replacement:
- Inspect the existing sensor’s threads and the hex size on the sensor body; typical pre- and post-cat sensors will have the same M18x1.5 threads, with a common 22 mm hex for removal.
- Check the OEM part number for your truck’s year and engine (for example, Toyota/Denso part numbers differ by model and year); reference the VIN on Toyota’s official parts database or a dealer.
- Bring the old sensor or measure the thread with a thread gauge or caliper, then match to a product’s thread specification before buying.
Bottom line: The standard Tacoma O2-sensor thread is M18x1.5, but always verify for your exact year, engine, and sensor location to avoid installation issues.
Summary
In most Toyota Tacoma models, oxygen sensors thread into the exhaust with an M18 x 1.5 metric size, applicable to both upstream and downstream sensors. Always confirm with the sensor’s part number or by measuring the existing threads to ensure compatibility, especially if you’re dealing with aftermarket sensors or older trims. This quick check can save time and prevent cross-threading or exhaust leaks.
