Introducing small amounts of hydrogen and oxygen into an internal combustion engine affects sensor readings based on the combustion products. An O2 sensor detects changes in oxygen levels, indicating whether the engine is running rich or lean, while a CO2 sensor remains unaffected by hydrogen addition. The engine's Powertrain Control Module (PCM) adjusts the air-fuel mixture based on these sensor readings, aiming for stoichiometric combustion. The specific impact on fuel mixture depends on the ratio of hydrogen and oxygen added; a lean mixture prompts the PCM to enrich with gasoline, while a rich mixture has the opposite effect. Ultimately, the engine's performance and efficiency can be optimized by understanding these dynamics.