You can use an oxygen sensor at the tailpipe to record air/fuel ratio data.

• A. Only for gas engines
• B. True
• C. False
• D. Never

Answer: (B)

Exhaust oxygen sensors measure how much O2 remains in the exhaust, and that information directly indicates whether the engine ran lean or rich relative to the ideal air/fuel mix. Placing the sensor in the tailpipe means you’re capturing the actual exhaust composition after combustion, which the engine’s control system uses to infer the air/fuel ratio (often expressed as lambda). This data is fundamental for monitoring and adjusting the mixture, and it’s a standard approach on gasoline engines (with variations for diesel and different sensor types, like wideband sensors, that give more precise readings across a wider range). So, using a tailpipe oxygen sensor to record air/fuel ratio data is correct.