can someone please tell me what this sensor dose, my car has a hesitation around 2000 rpm then runs fine after that. I've changed, plugs,maf front lambda sensor, ewage sti
thanks in advance

 

The rear O2 sensor sniffs the exhaust gasses after they have passed through the catalysts to make sure that the cats are working efficiently/correctly.

Neither the cat nor the sensor have an effect on fueling or ign, so would not cause a hessitation.

Phil

 

thanks for that
any other ideas