The 2016 Honda Pilot with a 3.5L V6 uses four oxygen sensors: two upstream sensors before the catalytic converter and two downstream sensors after it, one set for each exhaust bank.
Overview of the oxygen sensor system
In Honda's 3.5L V6 setup, the exhaust system is divided into two banks. Each bank has an upstream sensor (before the catalytic converter) and a downstream sensor (after the catalytic converter). The sensors feed data to the engine control unit to manage the air-fuel ratio and monitor catalytic efficiency.
Sensor locations by function
Upstream (pre-cat) sensors
These sensors monitor exhaust gases before they reach the catalytic converter. There are two sensors, one for each exhaust bank.
- Bank 1 Sensor 1 (B1S1) — located on the exhaust pipe/manifold side for Bank 1, just before the catalytic converter.
- Bank 2 Sensor 1 (B2S1) — located on the exhaust pipe/manifold side for Bank 2, just before the catalytic converter.
The upstream sensors provide real-time data used by the ECU to adjust the air-fuel mixture and emissions controls.
Downstream (post-cat) sensors
These sensors monitor exhaust after the catalytic converter to assess catalytic efficiency. There are two sensors, one for each exhaust bank.
- Bank 1 Sensor 2 (B1S2) — located downstream of the catalytic converter on Bank 1’s exhaust path.
- Bank 2 Sensor 2 (B2S2) — located downstream of the catalytic converter on Bank 2’s exhaust path.
The downstream sensors verify that the catalytic converter is functioning properly and help trigger diagnostic codes if needed.
Practical notes for locating and handling
To locate the sensors in person, safely raise the Pilot with a floor jack and support stands, then crawl under the vehicle. The sensors thread into the exhaust pipe and connect via wiring harnesses that run toward the engine bay. Use a proper O2 sensor socket (typically 22 mm) and disconnect the wiring harness before removal or replacement.
Summary
The 2016 Honda Pilot uses four oxygen sensors split between upstream and downstream positions on each exhaust bank: B1S1 and B2S1 before the catalytic converter, and B1S2 and B2S2 after it. Correct identification and careful handling are essential for accurate diagnostics and emissions compliance.