My ecu throws like 3 codes at me. one's the o2 sensor and the other is the speedo sensor probably due to the fact that my speedo isn't working rihgt now and a 3rd code i cant remember. is it true that ur check engine light is suppose to stay on no matter what u try? thanks for helping

 

That is false.

 

replace your o2 then hook up your speedo and then fix the problem with the third code....reset the ECU after you fix each problem to make sure the problem is in fact resolved.

when you fix them your light will go away.... good luck.