Hi,
I need your help to understand what my ECU does when the engine chech light is on.
Since 2 month, I'm driving with this light on, cause my O2 sensor on cat is broken (I'm speaking of the second O2 not that on the header).
In few days I'll install a new hight flow cat and O2 sensor, so I should solve the problem.
My question is: what does stock ECU do, meanwhile? I recordered more consumption... but also a reduced performance of my car, non only on track use, but also making an acceleration comparison with a friend with similar modification (the only difference are stock exhaust for me and HKS for him, and final gear ATS for me, should be an advantage, and stock ratio for him).

I know that stock ECU has 2 level of protection for the engine. Mine, should be the first one wiht reacher AF ratio but all rev (so I can understand consumption), but is it possible that I'm loosing some HP, with this emergency light on and current ECU setting?

Thanks

 

If i were you i would get a OBD II scan tool, to figure out exactly whats causing your CEL.