Oxygen sensors
Oxygen sensors
(OP)
Hi, most modern cars have two oxygen sensors on them,one usually in or close to the manifold for adjusting the air fuel mixture accordingly, what i would like to know is what the second oxygen sensor is for,as every body i have asked has a different opinion from,its a back up sensor to i havent a clue, i would like to know as i am only 24 and belive that you cannot diagnose a problem with a car un til you completely understand how all the components of an engine/electrical system work.
many thanks. matt
many thanks. matt





RE: Oxygen sensors
RE: Oxygen sensors
RE: Oxygen sensors
RE: Oxygen sensors
RE: Oxygen sensors
The Control Sensor sets the Air/Fuel mixture and ensures that the mixture is lean. Further leaning (mixture) will cause combustion problems. Even with this lean mixture, there is a small amount of unburnt fuel (hydrocarbons) present in the exhaust. These unburnt hydrocarbons are burnt off in the catalytic converter and the final exhaust is monitored by the downstream "Monitoring Sensor" which also checks for proper function of the cat convertor.
RE: Oxygen sensors
The upstream one is monitoring the exhaust and providing the necessary info for the ECU to adjust the Air/Fuel Ratio, the downstream one monitors both the performane of the catalytic converter, and also the performace of the 1st sensor. If the cat fails, a fault code will be set, and if the 1st sensor fails, the check engine light will come on and the second sensor will sort of substitute for the 1st one so that the engine can be "Limped" home.