Originally Posted by kpneverdies
thanks for your reply. but, what if you got the tune specific for HFC and CEL still comes up?
You have to run the codes and see what shows up. If you are still getting cat inefficiency codes then something is a miss with the tune.
Most tunes raise the thresholds to keep a CEL from coming on, even if you are catless. The CEL can still illuminate if something else is causing it.