How many O2 sensors does a 4Runner have?
The typical count is four O2 sensors on most Toyota 4Runner models with a V6 engine. The exact number can vary by year and engine configuration, but the standard setup generally involves two upstream sensors and two downstream sensors across two exhaust banks.
As Toyota has evolved the 4Runner through multiple generations, the engine and exhaust layout determine the sensor count. The following explains the common arrangement and notes where variations may occur, so readers can understand what to check on their specific vehicle.
Sensor arrangement basics
In a V6 4Runner with a dual-bank exhaust, each bank typically carries one upstream O2 sensor before the catalytic converter and one downstream sensor after the catalyst. This configuration provides monitoring of both catalysts and supports emissions control and engine management systems.
With two banks and one sensor per bank before and after the catalyst, the standard total remains four sensors. While this is the prevailing setup for most recent models, always verify against your vehicle’s VIN-specific service information to account for any regional or year-specific variations.
Model-year and engine variations
For the vast majority of US-market 4Runners in recent decades, the four-sensor arrangement is standard across the common V6 powertrains. Older or non-U.S. variants can differ, so it’s prudent to consult the official service manual or a dealer to confirm the exact count for a given VIN.
For practical verification, the O2 sensors are typically located along the exhaust system near the catalytic converters: two upstream ones positioned before each catalyst and two downstream ones after each catalyst. A quick visual check or a VIN lookup will confirm the precise configuration for a specific vehicle.
Summary
In most Toyota 4Runner configurations, especially those with V6 engines, there are four O2 sensors: two upstream sensors and two downstream sensors, one on each exhaust bank. While this is the standard setup, always verify with the vehicle’s service manual or dealer resources to account for any model-year or regional differences. Summary checks and VIN-based documentation will ensure you have the exact count for your particular 4Runner.
