What might an oscillating O2 sensor signal indicate?

An oscillating O2 sensor signal typically indicates that the sensor is functioning properly and is actively responding to changes in the air-fuel mixture entering the engine. A healthy O2 sensor oscillates between rich and lean conditions, helping the engine control unit (ECU) adjust the amount of fuel injected based on the oxygen content in the exhaust gases.

If the signal is oscillating as expected, this reflects that the sensor is accurately reading the combustion process and contributing effectively to the fuel management strategy. However, if the oscillation becomes erratic or the signal does not oscillate within the expected range, it might indicate an underlying issue that needs further investigation. This could suggest a potential malfunction in the sensor itself or in other components of the fuel management system, such as vacuum leaks, incorrect fuel pressure, or issues with engine performance.

In contrast, excessive fuel vapor or nonsensical readings would not typically result in the expected oscillation pattern. Similarly, failure of the CKP (Crankshaft Position) sensor affects ignition timing rather than the operation of the O2 sensor, making those choices less relevant in the context of identifying what an oscillating signal indicates.