jahudso2

You have 4 different 02 sensors in your car. 2 for the driver side and 2 for the passenger side. on each side, one sensor goes before the catalytic converter and one goes after. the one before the catalytic converter measures the air/fuel ratio of the engine and is necessary for proper engine running. the second set goes after the catalytic converters and monitors how the catalytic converters are working. if you remove the cats, but keep the sensors, it sets off an error which comes up as a check engine light because your car thinks your cats have failed. if you have an intake/tune package from brenspeed or bamachips, they most likely already turned your rear 02 sensors off and therefor it will not show a check engine light. you can drive your car around with no tune, but you will have the check engine light on all the time because your car will think the catalytic converters have gone bad.