They do this by measuring how much unburned oxygen is in the exhaust ... and fuel in the system, prompting it to inject more or less fuel into the engine. The second sensor measures oxygen ...

Replace exhaust system for better performance ... To connect to the exhaust, temporarily unscrew the oxygen sensor (the most forward one, if there are two). Make up a fitting that has the same ...

Bolted directly to the engine block, the exhaust manifold is the first section of a vehicle’s exhaust system ... in erroneous readings by the oxygen sensor, triggering a check engine light.