Quote:
Originally Posted by lookalikehuuh
I don't really see how an HJS cat would prevent the check engine codes from illuminating if you have no tune, since in theory they have a lower cell count catalyst, and these E90s are extremely finicky with catalyst efficiency.
Based on my research even the HJS cats will still fail smog checks and set codes, especially since they tend to be around the ~200-300cpsi where an OE cat is like 600-800cpsi. States like California still list the HJS cats as "Offroad only use" since they don't meet emissions standards.
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I've read the opposite and saw that HJS were the only ones that didn't pop the CEL because of the Euro4+/TUV certificiation. I might be wrong though.. *shrugs*