Two on the 2.4-liter four-cylinder, four on the 3.5-liter V6.
The 2012 Accord was offered with two engines, and the exhaust sensing setup mirrors that split: the inline-4 uses two sensors (one before and one after the catalytic converter), while the V6 uses four sensors (two banks, each with a pre- and post-cat sensor). The exact count depends on the engine in your specific car. Below is a detailed breakdown by engine option.
Engine options and sensor counts
2.4L inline-4 engine
In this configuration, the exhaust system uses two oxygen sensors: one upstream sensor before the catalytic converter and one downstream sensor after it.
- Upstream O2 sensor (pre-catalytic converter)
- Downstream O2 sensor (post-catalytic converter)
With this arrangement, the 2.4L Accord has two O2 sensors in total.
3.5L V6 engine
The 3.5-liter V6 configuration features four oxygen sensors—two sensors on each exhaust bank (one upstream and one downstream per bank).
- Bank 1 upstream O2 sensor
- Bank 1 downstream O2 sensor
- Bank 2 upstream O2 sensor
- Bank 2 downstream O2 sensor
Therefore, the 3.5L Accord has four O2 sensors in total.
Why it matters
Oxygen sensors are essential for monitoring exhaust gases, helping the engine control unit adjust fuel delivery and emissions to meet regulatory standards. If sensors fail or are not counting, you may see a check engine light, reduced fuel economy, or improper emissions readings. Replacing failed sensors requires matching the engine configuration and bank positioning.
Summary
In short, the number of O2 sensors on a 2012 Honda Accord depends on the engine: two sensors for the 2.4L inline-4, and four sensors for the 3.5L V6. Always verify the exact engine in your vehicle to determine the sensor count accurately.